Data vs. Models #4: Climates Changing

Köppen climate zones as they appear in the 21st Century.

Every day there are reports like this:

An annual breach of 2 degrees could happen as soon as 2030, according to climate model simulations, although there’s always the chance that climate models are slightly underestimating or overestimating how close we are to that date. Writing with fellow meteorologist Jeff Masters for Weather Underground, Bob Henson said the current spike means “we are now hurtling at a frightening pace toward the globally agreed maximum of 2.0°C warming over pre-industrial levels.”

That abstract, mathematically averaged world, the subject of so much media space and alarm, has almost nothing to do with the world where any of us live. Because nothing on our planet moves in unison.

Start with the hemispheres:

There’s clearly warming over the century, but also a divergence since about 1970, whereby NH rises much more than the SH.

Using round numbers, the Northern Hemisphere (NH) half of the total surface combines 20% land with 30% ocean, while the SH comprises 9% land with 41% ocean. With the oceans having huge heat capacities relative to the land, the NH has much more volatility in temperatures than does the SH. But more importantly, the trends in multi-decadal warming and cooling also differ.

Climates Are Found Down in the Weeds

The top-down global view needs to be supplemented with a bottom-up appreciation of the diversity of climates and their changes.

The ancient Greeks were the first to classify climate zones. From their travels and sea-faring experiences, they called the equatorial regions Torrid, due to the heat and humidity. The mid-latitudes were considered Temperate, including their home Mediterranean Sea. Further North and South, they knew places were Frigid.

Based on empirical observations, Köppen (1900) established a climate classification system which uses monthly temperature and precipitation to define boundaries of different climate types around the world. Since its inception, this system has been further developed (e.g. Köppen and Geiger, 1930; Stern et al., 2000) and widely used by geographers and climatologists around the world.

Köppen and Climate Change

The focus is on differentiating vegetation regimes, which result primarily from variations in temperature and precipitation over the seasons of the year. Now we have an interesting study that considers shifts in Köppen climate zones over time in order to identify changes in climate as practical and local/regional realities.

The paper is: Using the Köppen classification to quantify climate variation and change: An example for 1901–2010
By Deliang Chen and Hans Weiteng Chen
Department of Earth Sciences, University of Gothenburg, Sweden

Hans Chen has built an excellent interactive website (here): The purpose of this website is to share information about the Köppen climate classification, and provide data and high-resolution figures from the paper Chen and Chen, 2013: Using the Köppen classification to quantify climate variation and change: An example for 1901–2010 (pdf)

The Köppen climate classification consists of five major groups and a number of sub-types under each major group, as listed in Table 1. While all the major groups except B are determined by temperature only, all the sub-types except the two sub-types under E are decided based on the combined criteria relating to seasonal temperature and precipitation. Therefore, the classification scheme as a whole represents different climate regimes of various temperature and precipitation combinations.

Main characteristics of the Köppen climate major groups and sub-types:

Major group  Sub-types
A: Tropical Tropical rain forest: Af
Tropical monsoon: Am
Tropical wet and dry savanna: Aw, As
B: Dry Desert (arid): BWh, BWk
Steppe (semi-arid): BSh, BSk
C: Mild temperate Mediterranean: Csa, Csb, Csc
Humid subtropical: Cfa, Cwa
Oceanic: Cfb, Cfc, Cwb, Cwc
D: Snow Humid: Dfa, Dwa, Dfb, Dwb, Dsa, Dsb
Subarctic: Dfc, Dwc, Dfd, Dwd, Dsc, Dsd
E: Polar Tundra: ET
Ice cap: EF

Temporal Changes in Climate Zones

This study used a global gridded dataset with monthly mean temperature and precipitation, covering 1901–2010, which was produced and documented by Kenji Matsuura and Cort J. Willmott from Department of Geography, University of Delaware. Station data were compiled from different sources, including Global Historical Climatology Network version 2 (GHCN2) and the Global Surface Summary of Day (GSOD).The data and associated documentations can be found at http://climate.geog.udel.edu/climate/html_pages/Global2011/

In the maps below, the Köppen classification was applied on temperature and precipitation averaged over shorter time scales, from interannual to decadal and 30 year. The 30 year averages were calculated with an overlap of 20 years between each sub-period, while the interannual and decadal averages did not have overlapping years. Black regions indicate areas where the major Köppen type has changed at least once during 1901–2010 for a given time scale. Thus, the black regions are likely to be sensitive to climate variations, while the colored regions identify spatially stable regions.

Chen_and_Chen_2013fig2ab

Chen_and_Chen_2013fig2c

 

Major group Time scales
Interannual (%) Interdecadal (%) 30-year (%)
A                45.5                    89.0                 94.2
B                45.1                    85.2                 91.8
C                35.3                    77.4                 87.3
D                30.0                    83.3                 91.0
E                78.2                    92.8                 96.2

The table and images show that most places have had at least one entire year with temperatures and/or precipitation atypical for that climate.  It is much more unusual for abnormal weather to persist for ten years running.  At 30-years and more the zones are quite stable, such that is there is little movement at the boundaries with neighboring zones.

Over time, there is variety in zonal changes, albeit within a small range of overall variation:

Fig. 3. Temporal changes in the relative areas (area for 30 year windows minus the long term mean during 1901–2010, divided by the long term mean) of the five major Köppen groups. The 30 year window is moved forward with an interval of 10 years and the years showing the data indicates the middle of the 30 year window, e.g. 1995=1981–2010.

Chen and Chen Conclusions

By using a global gridded temperature and precipitation data over the period of 1901–2010, we reached the following conclusions:

  • Over the whole period (1901–2010), the mean climate distributions have a comparable pattern and portion with previous estimates. The five major groups A, B, C, D, E take up 19.4%, 28.4%, 14.6%, 22.1%, and 15.5% of the total land area on Earth respectively. Since the relative changes of the areas covered by the five major groups are all small on the 30 year time scale, the agreement indicates that the climate dataset used overall is of comparable quality with those used in other studies.
  • On the interannual, interdecadal, and 30 year time scales, the climate type for a given grid may shift from one type to another and the spatial stability decreases towards shorter time scales. While the spatially stable climate regions identified are useful for conservation and other purposes, the instable regions mark the transition zones which deserve special attention since they may have implications for ecosystems and dynamics of the climate system.
  • On the 30 year time scale, the dominating changes in the climate types over the whole period are that the arid regions occupied by group B (mainly type BWh) have expanded and the regions dominated by arctic climate (EF) have shrunk along with the global warming and regional precipitation changes.

Summary: The Myth of “Global” Climate Change

Climate is a term to describe a local or regional pattern of weather. There is a widely accepted system of classifying climates, based largely on distinctive seasonal variations in temperature and precipitation. Depending on how precisely you apply the criteria, there can be from 6 to 13 distinct zones just in South Africa, or 8 to 11 zones only in Hawaii.

Each climate over time experiences shifts toward warming or cooling, and wetter or drier periods. One example: Fully a third of US stations showed cooling since 1950 while the others warmed.  It is nonsense to average all of that and call it “Global Warming” because the net is slightly positive.  Only in the fevered imaginations of CO2 activists do all of these diverse places move together in a single march toward global warming.

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5 comments

  1. The paper by Belda et Al (2014) is probably the best to date in reconstructing the Koppen-Trewartha climate classification map for the valid reasons stated by the authors. The maps show the climate regions of the world (except Antarctica) for two periods, 1901-1931 and 1975-2005, based on a 30 minute grid, average area about 2500 km2, (About 50,000 grid cells cover 135 million km2, the land area of the Earth except Antarctica.)

    Between the two periods, 8% of the cells changed climate type. A scatter plot of distributions for the two periods, shows there is little divergence from the straight line passing through the origin and with slope unity. R-squared is 99.5.

    The paper does not discuss error bars. However, since the maps were prepared, the climate data has been revised to remove wet bias, an adjustment that would increase R2, indicating even less change than these maps show.

    In any other field of Earth science, using data with similar precision, we would claim confirmation of the null hypothesis that the two data sets separated by 75 years are not significantly different.

    Globally, the Earth has warmed a fraction of a degree Celsius, but the data do not support the claim that regional climates have changed enough since 1901-1930 to alter significantly the ecological zones defined by the Koppen-Trewartha system.

    Climate classification revisited from Köppen to Trewartha, Belda, M. et al, Climate Research, 2014
    http://www.int-res.com/articles/cr_oa/c059p001.pdf

    Like

    • Ron Clutz · May 18

      Thanks Frederick for that significant collaboration of stability of climates in the last century.

      Like

  2. hunter · May 18

    Wow, just wow.
    Once again we see that promoters of the so-called “climate consensus” are basing their extremism on a rejection of science, despite their loud claims to the contrary. And once again we see that the skeptic position- that nothing significant is changing in climate- is justified.

    Like

    • Ron Clutz · May 18

      The essence of the alarmist claim: Even though it hasn’t happened before, and isn’t happening now, it will surely happen in the future if we don’t do ____________ (fill in the blank).

      Like

  3. hunter · May 18

    Ron,
    Your point is true of all apocalyptic cults from my observation. The climate cult is just very popular these days, and veneers itself in science talk.

    Like

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