May Makes Both Land and Sea Cooler

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With apologies to Paul Revere, this post is on the lookout for cooler weather with an eye on both the Land and the Sea.  UAH has updated their tlt (temperatures in lower troposphere) dataset for May.   Previously I have done posts on their reading of ocean air temps as a prelude to updated records from HADSST3. This month also has a separate graph of land air temps because the comparisons and contrasts are interesting as we contemplate possible cooling in coming months and years.

Presently sea surface temperatures (SST) are the best available indicator of heat content gained or lost from earth’s climate system.  Enthalpy is the thermodynamic term for total heat content in a system, and humidity differences in air parcels affect enthalpy.  Measuring water temperature directly avoids distorted impressions from air measurements.  In addition, ocean covers 71% of the planet surface and thus dominates surface temperature estimates.  Eventually we will likely have reliable means of recording water temperatures at depth.

Recently, Dr. Ole Humlum reported from his research that air temperatures lag 2-3 months behind changes in SST.  He also observed that changes in CO2 atmospheric concentrations lag behind SST by 11-12 months.  This latter point is addressed in a previous post Who to Blame for Rising CO2?

After a technical enhancement to HadSST3 delayed March and April updates, May has just been posted, hopefully a signal the future months will also appear more promptly.  For comparison we can look at lower troposphere temperatures (TLT) from UAHv6 which are now posted for May. The temperature record is derived from microwave sounding units (MSU) on board satellites like the one pictured above. Last month also involved a change in UAH processing of satellite drift corrections, including dropping one platform which can no longer be corrected. The graphs below are taken from the new and current dataset.

The UAH dataset includes temperature results for air above the oceans, and thus should be most comparable to the SSTs. There is the additional feature that ocean air temps avoid Urban Heat Islands (UHI).  The graph below shows monthly anomalies for ocean temps since January 2015.

May ocean air temps dropped in all regions after April’s rise, resulting in the Global average back down below January 2019.  NH warming in February has been reversed, and April warming in SH and the Tropics is also gone.  The temps this May are warmer than 2018, but lower than 05/2017, and of course lower than 2016.

Land Air Temperatures Tracking Downward in Seesaw Pattern

We sometimes overlook that in climate temperature records, while the oceans are measured directly with SSTs, land temps are measured only indirectly.  The land temperature records at surface stations record air temps at 2 meters above ground.  UAH gives tlt anomalies for air over land separately from ocean air temps.  The graph updated for May is below.

The greater volatility of the Land temperatures was evident earlier, but has calmed down recently. Also the  NH dominates, having twice as much land area as SH.  Note how global peaks mirror NH peaks.  In January 2019 all Land air temps were close but have now diverged.  In May both SH and the Tropics dropped sharply (comparable to ocean temps), and the much larger NH land surface also cooled, pulling the Global anomaly down nearly 0.2C.  The Tropical land air temps could not be more different from 05/2018, yet the Global, NH and SH are much cooler.

TLTs include mixing above the oceans and probably some influence from nearby more volatile land temps.  Clearly NH and Global land temps have been dropping in a seesaw pattern, now more than 1C lower than the peak in 2016.  TLT measures started the recent cooling later than SSTs from HadSST3, but are now showing the same pattern.  It seems obvious that despite the three El Ninos, their warming has not persisted, and without them it would probably have cooled since 1995.  Of course, the future has not yet been written.

 

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Climate Changes Both Ways

The title comes from a news event last week when President Trump reminded Prince Charles of a natural truism:  Climate change goes both ways.  A media freak out ensued, as shown by this example from Newsweek.  Excerpt in italics with my bolds.

President Donald Trump said Wednesday he believes there has been a change in the weather due to climate change, but that “it changes both ways.”

The president then explained his views on the climate. “Don’t forget, it used to be called global warming, that wasn’t working, then it was called climate change, now it’s actually called extreme weather because with extreme weather you can’t miss,” the president said.

Environmental watchdog groups now advocate calling the phenomenon “climate catastrophe.”

It seemed to me that Trump is learning from his briefings with William Happer, and is finding the weak spots in the alarmist house of cards.  It also reminded me of a previous post describing the complexity of tracking climate change.  That essay is reprinted below because it reminds us that not only does climate change both ways, but also the warming and cooling can happen concurrently in some times and places.

Concurrent Climate Warming and Cooling

This post highlights recent interesting findings regarding past climate change in NH, Scotland in particular. The purpose of the research was to better understand how glaciers could be retreating during the Younger Dryas Stadia (YDS), one of the coldest periods in our Holocene epoch.

The lead researcher is Gordon Bromley, and the field work was done on site of the last ice fields on the highlands of Scotland. 14C dating was used to estimate time of glacial events such as vegetation colonizing these places. Bromely explains in article Shells found in Scotland rewrite our understanding of climate change at siliconrepublic. Excerpts in italics with my bolds.

By analysing ancient shells found in Scotland, the team’s data challenges the idea that the period was an abrupt return to an ice age climate in the North Atlantic, by showing that the last glaciers there were actually decaying rapidly during that period.

The shells were found in glacial deposits, and one in particular was dated as being the first organic matter to colonise the newly ice-free landscape, helping to provide a minimum age for the glacial advance. While all of these shell species are still in existence in the North Atlantic, many are extinct in Scotland, where ocean temperatures are too warm.

This means that although winters in Britain and Ireland were extremely cold, summers were a lot warmer than previously thought, more in line with the seasonal climates of central Europe.

“There’s a lot of geologic evidence of these former glaciers, including deposits of rubble bulldozed up by the ice, but their age has not been well established,” said Dr Gordon Bromley, lead author of the study, from NUI Galway’s School of Geography and Archaeology.

“It has largely been assumed that these glaciers existed during the cold Younger Dryas period, since other climate records give the impression that it was a cold time.”

He continued: “This finding is controversial and, if we are correct, it helps rewrite our understanding of how abrupt climate change impacts our maritime region, both in the past and potentially into the future.”

The recent report is Interstadial Rise and Younger Dryas Demise of Scotland’s Last Ice Fields G. Bromley A. Putnam H. Borns Jr T. Lowell T. Sandford D. Barrell  First published: 26 April 2018.(my bolds)

Abstract

Establishing the atmospheric expression of abrupt climate change during the last glacial termination is key to understanding driving mechanisms. In this paper, we present a new 14C chronology of glacier behavior during late‐glacial time from the Scottish Highlands, located close to the overturning region of the North Atlantic Ocean. Our results indicate that the last pulse of glaciation culminated between ~12.8 and ~12.6 ka, during the earliest part of the Younger Dryas stadial and as much as a millennium earlier than several recent estimates. Comparison of our results with existing minimum‐limiting 14C data also suggests that the subsequent deglaciation of Scotland was rapid and occurred during full stadial conditions in the North Atlantic. We attribute this pattern of ice recession to enhanced summertime melting, despite severely cool winters, and propose that relatively warm summers are a fundamental characteristic of North Atlantic stadials.

Plain Language Summary

Geologic data reveal that Earth is capable of abrupt, high‐magnitude changes in both temperature and precipitation that can occur well within a human lifespan. Exactly what causes these potentially catastrophic climate‐change events, however, and their likelihood in the near future, remains frustratingly unclear due to uncertainty about how they are manifested on land and in the oceans. Our study sheds new light on the terrestrial impact of so‐called “stadial” events in the North Atlantic region, a key area in abrupt climate change. We reconstructed the behavior of Scotland’s last glaciers, which served as natural thermometers, to explore past changes in summertime temperature. Stadials have long been associated with extreme cooling of the North Atlantic and adjacent Europe and the most recent, the Younger Dryas stadial, is commonly invoked as an example of what might happen due to anthropogenic global warming. In contrast, our new glacial chronology suggests that the Younger Dryas was instead characterized by glacier retreat, which is indicative of climate warming. This finding is important because, rather than being defined by severe year‐round cooling, it indicates that abrupt climate change is instead characterized by extreme seasonality in the North Atlantic region, with cold winters yet anomalously warm summers.

The complete report is behind a paywall, but a 2014 paper by Bromley discusses the evidence and analysis in reaching these conclusions. Younger Dryas deglaciation of Scotland driven by warming summers  Excerpts with my bolds.

Significance: As a principal component of global heat transport, the North Atlantic Ocean also is susceptible to rapid disruptions of meridional overturning circulation and thus widely invoked as a cause of abrupt climate variability in the Northern Hemisphere. We assess the impact of one such North Atlantic cold event—the Younger Dryas Stadial—on an adjacent ice mass and show that, rather than instigating a return to glacial conditions, this abrupt climate event was characterized by deglaciation. We suggest this pattern indicates summertime warming during the Younger Dryas, potentially as a function of enhanced seasonality in the North Atlantic.

Surface temperatures range from -30C to +30C

Fig. 1. Surface temperature and heat transport in the North Atlantic Ocean.  The relatively mild European climate is sustained by warm sea-surface temperatures and prevailing southwesterly airflow in the North Atlantic Ocean (NAO), with this ameliorating effect being strongest in maritime regions such as Scotland. Mean annual temperature (1979 to present) at 2 m above surface (image obtained using University of Maine Climate Reanalyzer, http://www.cci-reanalyzer.org). Locations of Rannoch Moor and the GISP2 ice core are indicated (yellow and red dots).

Thus the Scottish glacial record is ideal for reconstructing late glacial variability in North Atlantic temperature (Fig. 1). The last glacier resurgence in Scotland—the “Loch Lomond Advance” (LLA)—culminated in a ∼9,500-km2 ice cap centered over Rannoch Moor (Fig. 2A) and surrounded by smaller ice fields and cirque glaciers.

Fig. 2. Extent of the LLA ice cap in Scotland and glacial geomorphology of western Rannoch Moor. (A) Maximum extent of the ∼9,500 km2 LLA ice cap and larger satellite ice masses, indicating the central location of Rannoch Moor. Nunataks are not shown. (B) Glacial-geomorphic map of western Rannoch Moor. Distinct moraine ridges mark the northward active retreat of the glacier margin (indicated by arrow) across this sector of the moor, whereas chaotic moraines near Lochan Meall a’ Phuill (LMP) mark final stagnation of ice. Core sites are shown, including those (K1–K3) of previous investigations (14, 15).

When did the LLA itself occur? We consider two possible resolutions to the paradox of deglaciation during the YDS. First, declining precipitation over Scotland due to gradually increasing North Atlantic sea-ice extent has been invoked to explain the reported shrinkage of glaciers in the latter half of the YDS (18). However, this course of events conflicts with recent data depicting rapid, widespread imposition of winter sea-ice cover at the onset of the YDS (9), rather than progressive expansion throughout the stadial.

Loch Lomond

Furthermore, considering the gradual active retreat of LLA glaciers indicated by the geomorphic record, our chronology suggests that deglaciation began considerably earlier than the mid-YDS, when precipitation reportedly began to decline (18). Finally, our cores contain lacustrine sediments deposited throughout the latter part of the YDS, indicating that the water table was not substantially different from that of today. Indeed, some reconstructions suggest enhanced YDS precipitation in Scotland (24, 25), which is inconsistent with the explanation that precipitation starvation drove deglaciation (26).

We prefer an alternative scenario in which glacier recession was driven by summertime warming and snowline rise. We suggest that amplified seasonality, driven by greatly expanded winter sea ice, resulted in a relatively continental YDS climate for western Europe, both in winter and in summer. Although sea-ice formation prevented ocean–atmosphere heat transfer during the winter months (10), summertime melting of sea ice would have imposed an extensive freshwater cap on the ocean surface (27), resulting in a buoyancy-stratified North Atlantic. In the absence of deep vertical mixing, summertime heating would be concentrated at the ocean surface, thereby increasing both North Atlantic summer sea-surface temperatures (SSTs) and downwind air temperatures. Such a scenario is analogous to modern conditions in the Sea of Okhotsk (28) and the North Pacific Ocean (29), where buoyancy stratification maintains considerable seasonal contrasts in SSTs. Indeed, Haug et al. (30) reported higher summer SSTs in the North Pacific following the onset of stratification than previously under destratified conditions, despite the growing presence of northern ice sheets and an overall reduction in annual SST. A similar pattern is evident in a new SST record from the northeastern North Atlantic, which shows higher summer temperatures during stadial periods (e.g., Heinrich stadials 1 and 2) than during interstadials on account of amplified seasonality (30).

Our interpretation of the Rannoch Moor data, involving the summer (winter) heating (cooling) effects of a shallow North Atlantic mixed layer, reconciles full stadial conditions in the North Atlantic with YDS deglaciation in Scotland. This scenario might also account for the absence of YDS-age moraines at several higher-latitude locations (12, 36–38) and for evidence of mild summer temperatures in southern Greenland (11). Crucially, our chronology challenges the traditional view of renewed glaciation in the Northern Hemisphere during the YDS, particularly in the circum-North Atlantic, and highlights our as yet incomplete understanding of abrupt climate change.

Summary

Several things are illuminated by this study. For one thing, glaciers grow or recede because of multiple factors, not just air temperature. The study noted that glaciers require precipitation (snow) in order to grow, but also melt under warmer conditions. For background on the complexities of glacier dynamics see Glaciermania

Also, paleoclimatology relies on temperature proxies who respond to changes over multicentennial scales at best. C14 brings higher resolution to the table.

Finally, it is interesting to consider climate changing with respect to seasonality.  Bromley et al. observe that during Younger Dryas, Scotland shifted from a moderate maritime climate to one with more seasonal extremes like that of inland continental regions. In that light, what should we expect from cooler SSTs in the North Atlantic?

Note also that our modern warming period has been marked by the opposite pattern. Many NH temperature records show slight summer cooling along with somewhat stronger warming in winter, the net being the modest (fearful?) warming in estimates of global annual temperatures.

I’m with Trump on this one:  Climate shifts are not a matter of one-way warming, as we have been told.

 

N. Atlantic Keeps Its Cool

RAPID Array measuring North Atlantic SSTs.

For the last few years, observers have been speculating about when the North Atlantic will start the next phase shift from warm to cold. Given the way 2018 went and 2019 is following, this may be the onset.  First some background.

. Source: Energy and Education Canada

An example is this report in May 2015 The Atlantic is entering a cool phase that will change the world’s weather by Gerald McCarthy and Evan Haigh of the RAPID Atlantic monitoring project. Excerpts in italics with my bolds.

This is known as the Atlantic Multidecadal Oscillation (AMO), and the transition between its positive and negative phases can be very rapid. For example, Atlantic temperatures declined by 0.1ºC per decade from the 1940s to the 1970s. By comparison, global surface warming is estimated at 0.5ºC per century – a rate twice as slow.

In many parts of the world, the AMO has been linked with decade-long temperature and rainfall trends. Certainly – and perhaps obviously – the mean temperature of islands downwind of the Atlantic such as Britain and Ireland show almost exactly the same temperature fluctuations as the AMO.

Atlantic oscillations are associated with the frequency of hurricanes and droughts. When the AMO is in the warm phase, there are more hurricanes in the Atlantic and droughts in the US Midwest tend to be more frequent and prolonged. In the Pacific Northwest, a positive AMO leads to more rainfall.

A negative AMO (cooler ocean) is associated with reduced rainfall in the vulnerable Sahel region of Africa. The prolonged negative AMO was associated with the infamous Ethiopian famine in the mid-1980s. In the UK it tends to mean reduced summer rainfall – the mythical “barbeque summer”.Our results show that ocean circulation responds to the first mode of Atlantic atmospheric forcing, the North Atlantic Oscillation, through circulation changes between the subtropical and subpolar gyres – the intergyre region. This a major influence on the wind patterns and the heat transferred between the atmosphere and ocean.

The observations that we do have of the Atlantic overturning circulation over the past ten years show that it is declining. As a result, we expect the AMO is moving to a negative (colder surface waters) phase. This is consistent with observations of temperature in the North Atlantic.

Cold “blobs” in North Atlantic have been reported, but they are usually winter phenomena. For example in April 2016, the sst anomalies looked like this

But by September, the picture changed to this

And we know from Kaplan AMO dataset, that 2016 summer SSTs were right up there with 1998 and 2010 as the highest recorded.

As the graph above suggests, this body of water is also important for tropical cyclones, since warmer water provides more energy.  But those are annual averages, and I am interested in the summer pulses of warm water into the Arctic. As I have noted in my monthly HadSST3 reports, most summers since 2003 there have been warm pulses in the north atlantic.
amo december 2018
The AMO Index is from from Kaplan SST v2, the unaltered and not detrended dataset. By definition, the data are monthly average SSTs interpolated to a 5×5 grid over the North Atlantic basically 0 to 70N.  The graph shows the warmest month August beginning to rise after 1993 up to 1998, with a series of matching years since.  December 2016 set a record at 20.6C, but note the plunge down to 20.2C for  December 2018, matching 2011 as the coldest years  since 2000.  Because McCarthy refers to hints of cooling to come in the N. Atlantic, let’s take a closer look at some AMO years in the last 2 decades.

May is a transitional month, and does serve to show the pattern of North Atlantic pulse related to the ENSO events. In the last two decades, there were four El Nino events peaking in 1998, 2005, 2010 and 2016.  All those years appear in the May AMO record as over 20.4C, a level not previously reached in the North Atlantic. Note the dropoff to 20.2C the last two years.

This graph shows monthly AMO temps for some important years. The Peak years were 1998, 2010 and 2016, with the latter emphasized as the most recent. The other years show lesser warming, with 2007 emphasized as the coolest in the last 20 years. Note the red 2018 line is at the bottom of all these tracks.  The short black line shows that 2019 began slightly cooler than January 2018, and tracking closely since.

With all the talk of AMOC slowing down and a phase shift in the North Atlantic, it seems the annual average for 2018 confirms that cooling has set in.  Through December the momentum is certainly heading downward, despite the band of warming ocean  that gave rise to European heat waves last summer.

amo annual122018

 

Land and Sea Temps: April Southern Exposure

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With apologies to Paul Revere, this post is on the lookout for cooler weather with an eye on both the Land and the Sea.  UAH has updated their tlt (temperatures in lower troposphere) dataset for April.   Previously I have done posts on their reading of ocean air temps as a prelude to updated records from HADSST3. This month also has a separate graph of land air temps because the comparisons and contrasts are interesting as we contemplate possible cooling in coming months and years.

Presently sea surface temperatures (SST) are the best available indicator of heat content gained or lost from earth’s climate system.  Enthalpy is the thermodynamic term for total heat content in a system, and humidity differences in air parcels affect enthalpy.  Measuring water temperature directly avoids distorted impressions from air measurements.  In addition, ocean covers 71% of the planet surface and thus dominates surface temperature estimates.  Eventually we will likely have reliable means of recording water temperatures at depth.

Recently, Dr. Ole Humlum reported from his research that air temperatures lag 2-3 months behind changes in SST.  He also observed that changes in CO2 atmospheric concentrations lag behind SST by 11-12 months.  This latter point is addressed in a previous post Who to Blame for Rising CO2?

The April update to HadSST3 will hopefully appear later this month (March is yet to be posted).  In the meantime we can look at lower troposphere temperatures (TLT) from UAHv6 which are already posted for April. The temperature record is derived from microwave sounding units (MSU) on board satellites like the one pictured above. This month also involved a change in UAH processing of satellite drift corrections, including dropping one platform which can no longer be corrected. The graphs below are taken from the new and current dataset.

The UAH dataset includes temperature results for air above the oceans, and thus should be most comparable to the SSTs. There is the additional feature that ocean air temps avoid Urban Heat Islands (UHI).  The graph below shows monthly anomalies for ocean temps since January 2015.

Click on image to enlarge.

April ocean air temps rose in all regions, putting them back comparable with January 2019.  NH warming was slight, while stronger warming in SH and the Tropics pulled up the Global average.  The temps this April are warmer than 2018, nearly matching 2017, and of course much lower than 2016.

Land Air Temperatures Tracking Downward in Seesaw Pattern

We sometimes overlook that in climate temperature records, while the oceans are measured directly with SSTs, land temps are measured only indirectly.  The land temperature records at surface stations record air temps at 2 meters above ground.  UAH gives tlt anomalies for air over land separately from ocean air temps.  The graph updated for April is below.

The greater volatility of the Land temperatures was evident earlier, but has calmed down recently. Also the  NH dominates, having twice as much land area as SH.  Note how global peaks mirror NH peaks.  In January 2019 all Land air temps were close but have now diverged.  In April both SH and the Tropics warmed (comparable to ocean temps), but the much larger NH land surface cooled, pulling the Global anomaly down.  The Tropical land air temps could not be more different from a year ago, yet the Global is about the same.

TLTs include mixing above the oceans and probably some influence from nearby more volatile land temps.  Clearly NH and Global land temps have been dropping in a seesaw pattern, now more than 1C lower than the peak in 2016.  TLT measures started the recent cooling later than SSTs from HadSST3, but are now showing the same pattern.  It seems obvious that despite the three El Ninos, their warming has not persisted, and without them it would probably have cooled since 1995.  Of course, the future has not yet been written.

 

Climate Extrasensory Perception

A recent post Climate Hearsay featured an article by Ross McKitrick noting how climatists rely on charts and graphs to alarm people about temperature changes too small for them to notice otherwise.  For example, NOAA each month presents temperature measurements globally and broken down in various ways.  To illustrate McKitrick’s point, let’s look at the results for Quarter 1 of 2019, January through March.  Source: Global Climate Report

So the chart informs us that for this 3 month period, the whole world had its third warmest year out of the last 140 years!  2016 was a full 0.27℃ hotter on average over those 90 days.  Well, maybe not, because the error range is given as +/- 0.15℃.  So the difference this year from the record year 2016 might have been only a few 0.01℃, and no way you could have noticed that.  In fact where I live in Montreal, it didn’t seem like a warm year at all.

McKitrick also makes the point that claiming a country like Canada warmed more than twice the global average proves nothing.  In a cooling period, any place on land will cool faster than the global surface which is 71% ocean.  Same thing goes for warming: land temps change faster. For example, consider NOAA’s first quarter report on the major continents.

Surprise, surprise: North American temperatures ranked 38th out of 110 years, more than 2℃ cooler than 2016.  That’s more like what I experienced, though many days were much colder.  And browse the list of other land places: it was not that warm anywhere except for Oceania, with the land mass mostly in Australia.

Summary

Global warming/climate change is one of those everywhere, elsewhere phenomena.  Taking masses of temperatures and averaging them into a GMT (Global Mean Temperature Anomaly) is an abstraction, not anyone’s reality.  And in addition, minute changes in that abstraction are too small for anyone to sense.  Yet, modern civilization is presumed to be in crisis over 1.5℃ of additional warming, which we apparently already got in Canada and we are much better for it.

Some people worry Global Warming is changing how fast the Earth spins. Have you noticed?

Footnote:

Mike Hulme is a leading voice striking a rational balance between concern about the planet and careful deliberation over policy choices.  I have posted several of his articles, for example on extreme weather attribution and on attempts to link armed conflicts with climate change.  Pertinent to this post, Hulme has spoken out on the obsession with global temperature anomalies: See Obsessing Over Global Temperatures

Global temperature does not cause anything to happen. It has no material agency. It is an abstract proxy for the aggregated accumulation of heat in the surface boundary layer of the planet. It is far removed from revealing the physical realities of meteorological hazards occurring in particular places. And forecasts of global temperature threshold exceedance are even further removed from actionable early warning information upon which disaster risk management systems can work.

Global temperature offers the ultimate view of the planet—and of meteorological hazard—from nowhere.

And he has warned about the emergency rhetoric now on full display in the streets of major cities.  See Against Emergency Countdown

But as we argued a few years ago, declaring a climate emergency invokes a state of exception that carries many inherent risks: the suspension of normal governance, the use of coercive rhetoric, calls for ‘desperate measures’, shallow thinking and deliberation, and even militarization. To declare an emergency becomes an act of high moral and political significance, as it replaces the framework of ordinary politics with one of extraordinary politics.

In contrast, a little less rhetorical heat will allow for more cool-headed policy development. What is needed is clear-headed pragmatism, but without the Sword of Damocles hanging over these heads. Climate Pragmatism calls for accelerating technology innovation, including nuclear energy, for tightening local air quality standards, for sector-, regional- and local-level interventions to alter development trajectories and for major investments in improving female literacy. Not desperate measures called forth by the unstable politics of a state of emergency, but right and sensible things to do. And it is never too late to do the right thing.

 

Warmists Epic History Fail

Geologist Gregory Whitestone provides a climate history lesson for warmists who skipped history classes protesting against global warming.  His article at Town Hall is Ocasio-Cortez’s Climatology Lacks Historical Context. Excerpts in italics with my bolds. H/T Climate Depot.

When Sam Cooke sang “Don’t know much about history” in 1960 he could not have had U.S. Rep. Alexandria Ocasio-Cortez in mind, but only because she lives a half century later.

Whatever Ocasio-Cortez got from history classes during her time at Boston University, it wasn’t an appreciation of historical context because it is sorely lacking in her assertions about climate and its effect on humankind. She and others promoting the Green New Deal have the facts exactly backwards when they claim that warming temperatures are an existential threat to humanity.

Ocasio-Cortez recently warned in a House Oversight Committee hearing that the United States would have “blood on our hands” if legislation to tackle climate change was not passed. In questioning former Secretary of Defense Chuck Hagel, she alleged that “denial or even delaying in that action could cost us American life.”

Is that the case? Has increasing temperature been associated with negative impacts on the human condition? Common sense would seem to dictate that higher temperatures would lead to more drought and then to famine and ultimately to loss of life.

However, the story is different upon checking several thousands of years of extensive documentation covering the most recent warming trends to see how humans fared with temperatures like those predicted to occur by 2050 or 2100.

As it turns out, there is a great correlation between the rise and fall of temperature and the rise and fall of civilization, and the human experience is not the apocalypse you are being told to expect. Very consistently, throughout the last 3,500 years, humanity has prospered and thrived during warming periods, while the intervening colder periods witnessed crop failure, famine and mass depopulation. In fact, before climate science became politicized in the late 20th century, the warm eras were known as “Climate Optima” because both people and the Earth’s ecosystems benefited.

The last three warming trends corresponded with large advances in culture, science and technology. The Minoan (Bronze Age), Roman (Iron Age) and Medieval (High Middle Ages) periods were all much warmer than our current temperature and all benefited greatly from the rising temperature. Likely the most significant factor that allowed advances in civilization was a plentiful supply of food. Crops flourished and allowed time for the citizens of each culture to think, to dream and to invent.

Lucas van Valckenborch painted a cold winter landscape set near Antwerp, Belgium, in 1575, when Europe was in the midst of the Little Ice Age. Städel/Wikimedia Commons

Contrary to what we are being told by modern prophets of climate doom, it was the intervening cold that was devastating and led to the fall of empires and the collapse of civilizations. With names like the Greek Dark Ages, the Dark Ages and the Little Ice Age, these cold periods’ accompanying crop failure, famine, and mass depopulation were horrific for people.

The most recent and best documented cold period was the Little Ice Age (1250 – 1850 AD) which brought severe hardship, primarily in the northern latitudes. The combination of bitterly cold winters and cool, wet summers led to poor harvests, hunger and widespread death. Half the population of Iceland perished, and as much as one-third of humankind was decimated.

The worst cold of the Little Ice Age occurred in the late 17th century during a time known as the Maunder Minimum, which is linked to inactivity of the Sun. Based on the Central England Temperature record (the longest thermometer-based record) the depths of the cold were reached in the year 1695. For the next 40 years temperatures rose quickly and at several times the rate of warming measured in the 20th century.

The warming that began in the late 17th century continued for the next 300-plus years, ushering in an era of advancement unseen during any other period in humanity’s existence. It is what author W. Cleon Skousen called the “5,000 Year Leap” — five millennia of advances in communication, transportation, energy and exploration, and a doubling of the average length of human life, all condensed into less than 200 years. A myriad of factors were responsible, but it is certainly not clear that this progress would have occurred had Earth still been mired in the frigid temperatures of the Little Ice Age.

Last year, while Scott Pruitt was still the administrator of the EPA, he posed the question of how anyone could know what the ideal temperature of the Earth should be. Well known climate scientist Dr. Michael Mann of Penn State responded to Pruitt’s question by stating that the ideal temperature would be that which pre-dated the burning of fossil fuels. That temperature would put us squarely in the middle of the Little Ice Age’s devastating cold and history tells us that it turned out quite poorly.

History tells us that warming is very, very good, while cold is very, very bad.

Perhaps both Ocasio-Cortez and Mann should be labeled as “history deniers” for ignoring the true relationship between temperature and the human condition.

Footnote:  The obsession with a slight rise in average temperatures in the last 100 years is all the more remarkable for taking that warming totally out of context.
Any warming is good, even this small amount seen in the context of a year in the life of a typical American.  Moreover, the details of the statistics reveal that the rise is the result of cold months being warmer, while hotter months have cooled very slightly.  False Alarm.

Postscript (old soviet joke):  During soviet Russia era a professor addressed his history class, “I have good news and bad news about your final exam.  The good news is that all the questions are the same as last year.  The bad news:  Some of the answers are different.”

March Cools Seas More Than Land Warms

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With apologies to Paul Revere, this post is on the lookout for cooler weather with an eye on both the Land and the Sea.  UAH has updated their tlt (temperatures in lower troposphere) dataset for March.   Previously I have done posts on their reading of ocean air temps as a prelude to updated records from HADSST3. This month also has a separate graph of land air temps because the comparisons and contrasts are interesting as we contemplate possible cooling in coming months and years.

Presently sea surface temperatures (SST) are the best available indicator of heat content gained or lost from earth’s climate system.  Enthalpy is the thermodynamic term for total heat content in a system, and humidity differences in air parcels affect enthalpy.  Measuring water temperature directly avoids distorted impressions from air measurements.  In addition, ocean covers 71% of the planet surface and thus dominates surface temperature estimates.  Eventually we will likely have reliable means of recording water temperatures at depth.

Recently, Dr. Ole Humlum reported from his research that air temperatures lag 2-3 months behind changes in SST.  He also observed that changes in CO2 atmospheric concentrations lag behind SST by 11-12 months.  This latter point is addressed in a previous post Who to Blame for Rising CO2?

The March update to HadSST3 will appear later this month, but in the meantime we can look at lower troposphere temperatures (TLT) from UAHv6 which are already posted for March. The temperature record is derived from microwave sounding units (MSU) on board satellites like the one pictured above. This month also involved a change in UAH processing of satellite drift corrections, including dropping one platform which can no longer be corrected. The graphs below are taken from the new and current dataset.

The UAH dataset includes temperature results for air above the oceans, and thus should be most comparable to the SSTs. There is the additional feature that ocean air temps avoid Urban Heat Islands (UHI).  The graph below shows monthly anomalies for ocean temps since January 2015.

Open image in new tab to enlarge.

The anomalies over the entire ocean dropped to the same value, 0.11C  in August.  Warming in previous months was erased, and September added very little warming back. In October and November NH and the Tropics rose, joined by SH.  In December 2018 all regions cooled resulting in a global drop of nearly 0.1C. The upward bump in January in SH was reversed in February.  Despite some February warming in both NH and the Tropics, the Global anomaly cooled. Now in March the cooling appears in all regions resulting in a global decline in SST anomaly of 01C since 01/2019. Except for the Tropics, the ocean SSTs match those of 2015.

Land Air Temperatures Tracking Downward in Seesaw Pattern

We sometimes overlook that in climate temperature records, while the oceans are measured directly with SSTs, land temps are measured only indirectly.  The land temperature records at surface stations record air temps at 2 meters above ground.  UAH gives tlt anomalies for air over land separately from ocean air temps.  The graph updated for March is below.

The greater volatility of the Land temperatures was evident earlier, but has calmed down recently. Also the  NH dominates, having twice as much land area as SH.  Note how global peaks mirror NH peaks.  In November air over NH land Global and surfaces bottomed.despite the Tropics.  By January  all regions had almost the same anomaly. Now in March an upward bump in NH has pulled the Global anomaly up, and both are comparable to early 2015.  SH and the Tropics air over land are currently matching other regions, in contrast to starting 2015 much cooler.

TLTs include mixing above the oceans and probably some influence from nearby more volatile land temps.  Clearly NH and Global land temps have been dropping in a seesaw pattern, now more than 1C lower than the peak in 2016.  TLT measures started the recent cooling later than SSTs from HadSST3, but are now showing the same pattern.  It seems obvious that despite the three El Ninos, their warming has not persisted, and without them it would probably have cooled since 1995.  Of course, the future has not yet been written.

 

About Canadian Warming: Just the Facts

Just in time for the Trudeau carbon tax taking effect, we have all the media trumpeting “Canada Warming Twice as Fast as Global Rate–Effectively Irreversible.”  That was written by some urban-dwelling climate illiterates who are woefully misinformed.  Let’s help them out with some facts surprising to people who don’t get out much.  Unfortunately ignored this week was an informative CBC publication that could have spared us “fake news” spewing across the land, from Bonavista to Vancouuver Island, as the song says.

Surprising Facts About Canada are presented in a CBC series 10 Strange Facts About Canada’s Climate  Excerpts below provide highlights in italics with my bolds.

Through blistering cold winters to hot muggy summers; torrential rain, blinding snowstorms, deadly tornados and scorching drought, Canadians experience some of the planet’s most diverse weather systems.  [ Uh oh, averaging all of that could be a problem]

Canada is as tall as it is wide, creating a wide range of climate conditions.

Canada has the largest latitude range of any country on the planet. Our southern border lies at the same latitude as northern California, while our northern edge reaches right to the top of the world. It’s rarely the same season in the same place at the same time. In early April, the Arctic may still be in the throes of a frigid winter, while the south can experience summer-like temperatures. No doubt, our weather forecasters are the busiest in the world!

Canada has an ‘iceberg alley’.

Pieces of glaciers from the coast of Greenland are picked up by the Labrador Current, a counter-clockwise vortex of waters in the North Atlantic Ocean. Those broken pieces become icebergs that float in the sea off northeast Newfoundland where Fogo Island lies. Navigating the area is risky for ships; in fact this is where the mighty Titanic sank in 1912. But it’s a boon to tourism. Iceberg seekers flock to the area to watch (safely) from the shore and boast about drinking 10,000-year-old fresh water taken from an iceberg floating in the ocean.

Niagra Falls (the Canadian side)

Canada is (really) cold.

It’s certainly not surprising to most Canadians that we are tied with Russia for the title of ‘coldest nation in the world.’ Over our vast country, we have an average daily temperature of -5.6C. This is deadly cold. More of us — about 108 — die from exposure to extreme cold than from any other natural event. And that’s not counting Canadian wildlife who are more susceptible to Canada’s icy climate than we are.

Calgary Golfer February 9, 2016.

Every winter, southern Alberta is the ‘Chinook’ capital.

For six months — from November to May — warm dry winds rush down the slope of the Rocky Mountains towards southern Alberta. Often moving at hurricane-force speeds of 120 km per hour, they can bring astonishing temperature changes and melt ice within a couple of hours. In 1962 Pincher Creek saw a record temperature rise of 41C, from -19 to 22 in just one hour. Chinook is also known as the ‘ice-eater’ among locals who appreciate the break from winter that the winds provide.

Newfoundland is the foggiest place in the world.

At the Grand Banks off Newfoundland, the cold water from the Labrador Current from the north meets the warmer Gulf Stream from the south. The result is a whopping 206 days of fog a year. In the summer, it’s foggy 84 per cent of the time! It’s also the richest fishery in the world, the fog is a serious hazard to ships in the region.

Aerial view of the Haughton-Mars Project Research Station (HMPRS) on Devon Island, Nunavut, Arctic Canada is shown in this undated handout image.

Canada’s North is actually a desert

Canada’s North is very cold and dry with very little precipitation, ranging from 10-20 cm a year. Temperatures average below freezing most of the year. Together, they limit the diversity of plants and animals found in the North. And it’s huge: this polar desert covers one seventh of Canada’s total land mass.

In 1816, Canada didn’t have a summer.

If winter in Canada weren’t bad enough, in 1816 the country’s eastern population were sledding in June and thawing water cisterns in July. Trees shed their leaves and there were reports of migratory birds dropping dead in the streets.

Over in Europe, the weird weather stoked anti-American sentiment. People opposed to emigration said that North America was inhospitable and getting colder every year.

Representation of Mount Tambora 1815 eruption in Indonesia.

Ironically, as eastern Canada stayed cool, the Arctic warmed, creating flotillas of icebergs off the coasts of Nova Scotia and Newfoundland. At the time, it was thought that the icebergs were the cause of the cooling, like a giant glass of iced lemonade. What was the real reason? In 1815, the Tambora volcano erupted in Indonesia, spewing tonnes of ash and dust into the air. Less sunlight reached the earth and this caused the planet’s surface to cool. The volcanic eruption changed the climate in different ways around the world, but Eastern Canadians were treated to the summer that just didn’t come.

The Prairies face brutal temperature extremes.

It’s no surprise that Regina, Saskatchewan — which lies smack in the middle of Canada’s prairies — lays claim to both the country’s lowest recorded temperature, -50C on January 1, 1885 and the highest, 43.3C on July 5, 1937. Without the moderating effects of a large body of water, Canada’s Prairies are vulnerable to some of the worst weather Canada has to offer.

Hopewell Rocks at the Bay of fundy. Photo: gregstokinger

The Bay of Fundy has the largest tides in the world.

Twice each day, 160 billion tonnes of seawater flow in and out of this small area in Nova Scotia — more than the combined flow of the world’s freshwater rivers. The tides reach a peak of 16 metres (as high as a five-storey building) and take about six hours to come in. The most extreme tides in the Bay occur twice each month when the earth, moon and sun are in alignment and together they create a larger-than-usual gravitational pull on the ocean, creating a “spring tide” (not to be confused with the season spring).

Lightning over Lake St. Clair Photo: seebest

Windsor is the thunderstorm capital of Canada.

Hot, humid air from the Gulf of Mexico funnels up through Windsor and the Western Basin of Lake Erie creating the perfect conditions for thunderstorms. About 251 lightning flashes per 100 square kilometres happen every year when small pieces of frozen raindrops collide within thunderclouds. The clouds fill with electrical charges that are eventually funnelled to the ground as lightning.

Summary

With all that going on, all the variety of temperature, precipitation, weather events and seasonalities, no one noticed it had warmed much, and would be grateful if it had.  With all the alarms sounding about the Arctic meltdown in the last decades, let’s consider the best long-service stations in the far north.

According to the “leaked report”, Canada’s annual average temperature over land has warmed 1.7 C when looking at the data since 1948. But that claim is misleading when recent data is considered.

Over the past 25 years, since scientists began to warn that the planet was warming in earnest, there has not been any warming when one looks at the untampered data provided by the Japan meteorology Agency (JMA) that were measured by 9 different stations across Canada. These 9 stations have the data dating back to around 1983 or 1986, so I used their datasats.

Looking at the JMA database and plotting the stations with longer term recording, we have the following chart:

Though temperatures over Canada no doubt have risen over the past century, there has not been any real warming in over 25 years. Rather, there’s been slight cooling, though not statistically significant. Clearly there hasn’t been any Canadian warming recently.

So it is misleading — to say the least — to give the impression that Canada warming has been accelerating. Thanks to Kirye for posting this at No Tricks Zone

See also Cold Summer in Nunavut

N. Atlantic Starts Cold in 2019

RAPID Array measuring North Atlantic SSTs.

Update April 10, 2019  March AMO Results now available and included in Decadal graph below.

For the last few years, observers have been speculating about when the North Atlantic will start the next phase shift from warm to cold. Given the way 2018 went, this may be the onset.  First some background.

Source: Energy and Education Canada

An example is this report in May 2015 The Atlantic is entering a cool phase that will change the world’s weather by Gerald McCarthy and Evan Haigh of the RAPID Atlantic monitoring project. Excerpts in italics with my bolds.

This is known as the Atlantic Multidecadal Oscillation (AMO), and the transition between its positive and negative phases can be very rapid. For example, Atlantic temperatures declined by 0.1ºC per decade from the 1940s to the 1970s. By comparison, global surface warming is estimated at 0.5ºC per century – a rate twice as slow.

In many parts of the world, the AMO has been linked with decade-long temperature and rainfall trends. Certainly – and perhaps obviously – the mean temperature of islands downwind of the Atlantic such as Britain and Ireland show almost exactly the same temperature fluctuations as the AMO.

Atlantic oscillations are associated with the frequency of hurricanes and droughts. When the AMO is in the warm phase, there are more hurricanes in the Atlantic and droughts in the US Midwest tend to be more frequent and prolonged. In the Pacific Northwest, a positive AMO leads to more rainfall.

A negative AMO (cooler ocean) is associated with reduced rainfall in the vulnerable Sahel region of Africa. The prolonged negative AMO was associated with the infamous Ethiopian famine in the mid-1980s. In the UK it tends to mean reduced summer rainfall – the mythical “barbeque summer”.Our results show that ocean circulation responds to the first mode of Atlantic atmospheric forcing, the North Atlantic Oscillation, through circulation changes between the subtropical and subpolar gyres – the intergyre region. This a major influence on the wind patterns and the heat transferred between the atmosphere and ocean.

The observations that we do have of the Atlantic overturning circulation over the past ten years show that it is declining. As a result, we expect the AMO is moving to a negative (colder surface waters) phase. This is consistent with observations of temperature in the North Atlantic.

Cold “blobs” in North Atlantic have been reported, but they are usually winter phenomena. For example in April 2016, the sst anomalies looked like this

But by September, the picture changed to this

And we know from Kaplan AMO dataset, that 2016 summer SSTs were right up there with 1998 and 2010 as the highest recorded.

As the graph above suggests, this body of water is also important for tropical cyclones, since warmer water provides more energy.  But those are annual averages, and I am interested in the summer pulses of warm water into the Arctic. As I have noted in my monthly HadSST3 reports, most summers since 2003 there have been warm pulses in the north atlantic.
amo december 2018
The AMO Index is from from Kaplan SST v2, the unaltered and not detrended dataset. By definition, the data are monthly average SSTs interpolated to a 5×5 grid over the North Atlantic basically 0 to 70N.  The graph shows the warmest month August beginning to rise after 1993 up to 1998, with a series of matching years since.  December 2016 set a record at 20.6C, but note the plunge down to 20.2C for  December 2018, matching 2011 as the coldest years  since 2000.  Because McCarthy refers to hints of cooling to come in the N. Atlantic, let’s take a closer look at some AMO years in the last 2 decades.

This graph shows monthly AMO temps for some important years. The Peak years were 1998, 2010 and 2016, with the latter emphasized as the most recent. The other years show lesser warming, with 2007 emphasized as the coolest in the last 20 years. Note the red 2018 line is at the bottom of all these tracks.  The short black line shows that 2019 began slightly cooler than January 2018  The February average AMO matched the low SST of the previous year, 0.14C lower than the peak year February 2017. March 2019 is also slightly lower than 2018  and 0.06C lower than peak year March 2016.

With all the talk of AMOC slowing down and a phase shift in the North Atlantic, it seems the annual average for 2018 confirms that cooling has set in.  Through December the momentum is certainly heading downward, despite the band of warming ocean  that gave rise to European heat waves last summer.

amo annual122018

natlssta

cdas-sflux_sst_atl_1

 

De Nada Ocean SSTs in February

The best context for understanding decadal temperature changes comes from the world’s sea surface temperatures (SST), for several reasons:

  • The ocean covers 71% of the globe and drives average temperatures;
  • SSTs have a constant water content, (unlike air temperatures), so give a better reading of heat content variations;
  • A major El Nino was the dominant climate feature in recent years.

HadSST is generally regarded as the best of the global SST data sets, and so the temperature story here comes from that source, the latest version being HadSST3.  More on what distinguishes HadSST3 from other SST products at the end.

The Current Context

The chart below shows SST monthly anomalies as reported in HadSST3 starting in 2015 through February 2019. For some reason, it took almost a whole month to publish the updated dataset.

A global cooling pattern is seen clearly in the Tropics since its peak in 2016, joined by NH and SH cycling downward since 2016.  2018 started with slow warming after the low point of December 2017, led by steadily rising NH, which peaked in September and cooled since.  The Tropics rose steadily until November, and are now cooling as well.  With a little warming in SH, the Global anomaly is virtually unchanged last month.

All regions are about the same as 02/2017 and 02/2015, but much cooler than 02/2016.  The February Global anomaly is 0.09 lower than 2016;  NH is 0.06 lower, SH is 0.09 lower and the Tropics  are down 0.43, or 50% from 02/2016. The rise in the Tropics had suggested a possible El Nino, but is now cooling down and better described as De Nada.

Note that higher temps in 2015 and 2016 were first of all due to a sharp rise in Tropical SST, beginning in March 2015, peaking in January 2016, and steadily declining back below its beginning level. Secondly, the Northern Hemisphere added three bumps on the shoulders of Tropical warming, with peaks in August of each year.  A fourth NH bump was lower and peaked in September 2018.  Also, note that the global release of heat was not dramatic, due to the Southern Hemisphere offsetting the Northern one.

The annual SSTs for the last five years are as follows:

Annual SSTs Global NH SH  Tropics
2014 0.477 0.617 0.335 0.451
2015 0.592 0.737 0.425 0.717
2016 0.613 0.746 0.486 0.708
2017 0.505 0.650 0.385 0.424
2018 0.480 0.620 0.362 0.369

2018 annual average SSTs across the regions are close to 2014, slightly higher in SH and much lower in the Tropics.  The SST rise from the global ocean was remarkable, peaking in 2016, higher than 2011 by 0.32C.

A longer view of SSTs

The graph below  is noisy, but the density is needed to see the seasonal patterns in the oceanic fluctuations.  Previous posts focused on the rise and fall of the last El Nino starting in 2015.  This post adds a longer view, encompassing the significant 1998 El Nino and since.  The color schemes are retained for Global, Tropics, NH and SH anomalies.  Despite the longer time frame, I have kept the monthly data (rather than yearly averages) because of interesting shifts between January and July.

Open image in new tab to enlarge.

1995 is a reasonable starting point prior to the first El Nino.  The sharp Tropical rise peaking in 1998 is dominant in the record, starting Jan. ’97 to pull up SSTs uniformly before returning to the same level Jan. ’99.  For the next 2 years, the Tropics stayed down, and the world’s oceans held steady around 0.2C above 1961 to 1990 average.

Then comes a steady rise over two years to a lesser peak Jan. 2003, but again uniformly pulling all oceans up around 0.4C.  Something changes at this point, with more hemispheric divergence than before. Over the 4 years until Jan 2007, the Tropics go through ups and downs, NH a series of ups and SH mostly downs.  As a result the Global average fluctuates around that same 0.4C, which also turns out to be the average for the entire record since 1995.

2007 stands out with a sharp drop in temperatures so that Jan.08 matches the low in Jan. ’99, but starting from a lower high. The oceans all decline as well, until temps build peaking in 2010.

Now again a different pattern appears.  The Tropics cool sharply to Jan 11, then rise steadily for 4 years to Jan 15, at which point the most recent major El Nino takes off.  But this time in contrast to ’97-’99, the Northern Hemisphere produces peaks every summer pulling up the Global average.  In fact, these NH peaks appear every July starting in 2003, growing stronger to produce 3 massive highs in 2014, 15 and 16.  NH July 2017 was only slightly lower, and a fifth NH peak still lower in Sept. 2018.  Note also that starting in 2014 SH plays a moderating role, offsetting the NH warming pulses. (Note: these are high anomalies on top of the highest absolute temps in the NH.)

What to make of all this? The patterns suggest that in addition to El Ninos in the Pacific driving the Tropic SSTs, something else is going on in the NH.  The obvious culprit is the North Atlantic, since I have seen this sort of pulsing before.  After reading some papers by David Dilley, I confirmed his observation of Atlantic pulses into the Arctic every 8 to 10 years.

But the peaks coming nearly every summer in HadSST require a different picture.  Let’s look at August, the hottest month in the North Atlantic from the Kaplan dataset.
AMO August 2018

The AMO Index is from from Kaplan SST v2, the unaltered and not detrended dataset. By definition, the data are monthly average SSTs interpolated to a 5×5 grid over the North Atlantic basically 0 to 70N. The graph shows warming began after 1992 up to 1998, with a series of matching years since. Because the N. Atlantic has partnered with the Pacific ENSO recently, let’s take a closer look at some AMO years in the last 2 decades.

This graph shows monthly AMO temps for some important years. The Peak years were 1998, 2010 and 2016, with the latter emphasized as the most recent. The other years show lesser warming, with 2007 emphasized as the coolest in the last 20 years. Note the red 2018 line is at the bottom of all these tracks. The short black line shows that 2019 began slightly cooler than January 2018,  and in February matched the low SST of the previous year.

Summary

The oceans are driving the warming this century.  SSTs took a step up with the 1998 El Nino and have stayed there with help from the North Atlantic, and more recently the Pacific northern “Blob.”  The ocean surfaces are releasing a lot of energy, warming the air, but eventually will have a cooling effect.  The decline after 1937 was rapid by comparison, so one wonders: How long can the oceans keep this up? If the pattern of recent years continues, NH SST anomalies will likely cool in coming months.  Once again, ENSO will probably determine the outcome.

Postscript:

In the most recent GWPF 2017 State of the Climate report, Dr. Humlum made this observation:

“It is instructive to consider the variation of the annual change rate of atmospheric CO2 together with the annual change rates for the global air temperature and global sea surface temperature (Figure 16). All three change rates clearly vary in concert, but with sea surface temperature rates leading the global temperature rates by a few months and atmospheric CO2 rates lagging 11–12 months behind the sea surface temperature rates.”

Footnote: Why Rely on HadSST3

HadSST3 is distinguished from other SST products because HadCRU (Hadley Climatic Research Unit) does not engage in SST interpolation, i.e. infilling estimated anomalies into grid cells lacking sufficient sampling in a given month. From reading the documentation and from queries to Met Office, this is their procedure.

HadSST3 imports data from gridcells containing ocean, excluding land cells. From past records, they have calculated daily and monthly average readings for each grid cell for the period 1961 to 1990. Those temperatures form the baseline from which anomalies are calculated.

In a given month, each gridcell with sufficient sampling is averaged for the month and then the baseline value for that cell and that month is subtracted, resulting in the monthly anomaly for that cell. All cells with monthly anomalies are averaged to produce global, hemispheric and tropical anomalies for the month, based on the cells in those locations. For example, Tropics averages include ocean grid cells lying between latitudes 20N and 20S.

Gridcells lacking sufficient sampling that month are left out of the averaging, and the uncertainty from such missing data is estimated. IMO that is more reasonable than inventing data to infill. And it seems that the Global Drifter Array displayed in the top image is providing more uniform coverage of the oceans than in the past.

uss-pearl-harbor-deploys-global-drifter-buoys-in-pacific-ocean

USS Pearl Harbor deploys Global Drifter Buoys in Pacific Ocean