by Rud Istvan
One of the firmer catastrophic anthropogenic global warming (CAGW) predictions made by IPCC AR4 WG2 was an alarming increase in species extinctions.
§4.4.11 Global synthesis including impacts on biodiversity was quite specific. If warming reached 3°C above pre-industrial levels (projected absent serious mitigation) 21-52% of all species were committed to extinction (not necessarily yet extinct) by 2100. This official finding was based on 78 conclusions from 57 peer-reviewed papers on climate change impacts on biodiversity, all listed in WG2 table 4.1. It appears to be overwhelming scientific evidence. It isn’t. There are no bodies.
Despite the dire IPCC AR4 CAGW extinction prediction, there has yet to be a single climate change extinction “body”. Polar bears are thriving. So are Adélie penguins in Antarctica.[i], [ii] Costa Rica’s golden toad was done in by the fungal disease chytridiomycosis, not AGW.[iii] Australia’s white lemuroid ringtail possum lives on in Queensland forest preserves. [iv] A contemporary peer reviewed criticism of AR4 WG2 extinctions concluded its abstract by observing:
“We note a Quaternary conundrum: While current empirical and theoretical ecological results suggest that many species could be at risk from global warming, during the recent ice ages surprisingly few species became extinct.” [v]
In other words, there are no bodies.
So how did IPCC AR4 WG2 reach its supposedly scientific conclusion? A bit of forensics starting with their figure 4.4 reveals the very dubious IPCC basis.
The highlighted temperature rise of 1.6°C 9-31% global species loss is supported by findings 5-7; the 3°C 21-52% global species loss is supported by findings 46-52. Most other findings discuss areal changes in regional habitat, or single species impacts in specific ecosystems, for example the highlighted polar bears.
This IPCC figure says that only 10 of the 78 references listed in table 4.1 actually support any global extinction estimate. The 10 relevant references are:
These excerpts suggest IPCC intent to deceive in 4.4. The low temperature estimate depends on only one reference, #1, not three. The high temperature global estimate also depends on just #1, not the seven cited. The entire IPCC AR4 global extinction estimates come down to a single peer reviewed paper, #1 Thomas 2004. [vi] In fact, 13 of the listed 78 IPCC references are this single paper, including all numerical WG2 global extinction estimates except for freshwater fish. And fresh water fish weren’t globally risked in that sole other paper, as IPCC misrepresented. [vii] This singularity merits closer scrutiny.
Thomas et. al. used mathematical models of the exponential relationship between species number and species areal extent within ecosystem ‘climate envelopes’ (Number of species S=c Az. Larger areas/envelopes A have more species; smaller areas/envelopes have fewer species. So as climate envelopes shrink, ‘extinctions’ rise since the equation says there are fewer species in smaller areas.) The exponent chosen for estimating all species types in all regions was Z=0.25, which a footnote said was empirically appropriate for tropical birds given logging deforestation.[viii] That is a dubious exponent value for all species including plants, and for climates outside the tropics. A stronger peer reviewed methodological critique concluded this equation always overstates extinctions, no matter what exponent ‘Z’ is plugged in. [ix]
HadCM2 was used to model temperature and rainfall change in regional climate envelopes for 2050, and hence future regional envelope areas A. Modeled regional climate results are dubious because of well-known problems with regionally downscaled GCMs. [x] HadCM2 was also run “hot”. Supplemental information table 1 says a global mean anomaly of 2.6°C in 2050 for SRES A2, (with 2.1-3.9°C by modeled region). That is nearly twice what IPCC AR4 said (SPM Figure 5 scenario A2 ≈1.6°C), or Figure 4.4 as graphed (1.5°C-1.7°C).
Using a dubious Z in a faulty equation with a hot climate input, this paper assessed 20% of Earth’s terrestrial surface in 7 specific regions, using seven groups of regionally endemic species including 112 mammals, 238 birds, 69 butterflies, and 607 plants. The SI does not identity the 1103 species assessed. Those endemic results were extrapolated without modification to the world, a ‘hidden’ selection bias significantly overstating general CAGW extinction risk.
Despite the missing SI species information, some things can be inferred about the paper’s endemic species selection using the largest animal group, birds (since they are passionately well studied by ‘birders’, and the basis for ‘Z’). ‘Small’ Endemic Bird Areas (EBAs) account for about 2500 of the known 10518 avian species. EBAs are intensely monitored by birders since half of all EBA bird species are already classified as threatened by IUCN. Table 1 says endemic birds were assessed in four regions: Queensland Australia, South Africa, Europe, and Mexico. Queensland has 630 bird species of which 20-22 are endemic; table 1 says 13 were used in the study. South Africa has 843 species of which 19 are endemic; 5 were used. Europe has about 800 species of which only about 10 are endemic; 34 were used. Mexico has 1054 species, 145 EBA’s, and 98 endemic species; 186 were used. The paper selected 238 out of the 3019 bird species known in the studied regions, 8%. The selection is explicitly weighted (149/238) 63% endemic birds—half already listed as threatened for habitat reasons. That evidences selection bias. It is not subtle, merely somewhat hidden.
Queensland can be scrutinized even more closely. All 20-22 endemic species (sources disagree as to exactly how many are just in Queensland) have limited ranges and specialized habitats just like the lemuroid ringtail possum. For example, Victoria’s Riflebird (the Duwuduwu) is a bird of paradise found only in Atherton Tableland (Plateau) remnant rainforests. Half (11) of Queensland’s endemic birds live only in those high cool rainforest remnants, viewed from the Mt. Bartle Frere trailhead above Atherton Tableland. Just like lemuroid ringtails.
Select only range limited endemic birds already surviving only in remnant ecosystem rainforests, regionally downsize HadCM2 to model overheating and reduced rainfall in them, and voila! Avian climate change extinction risk increases—a lot. Queensland birds were the highest risked of all animal species/regions in the paper’s Table 1 assessments. Even if true, this finding would not extrapolate to the other 610 Australian birds inhabiting a broader range and larger climate envelope than remnant Queensland high, cool rainforests. The paper’s bird result is methodologically overstated even for EBA species. It does not apply at all to the other three fourths of bird species with larger climate envelopes. Yet it was. Then that overstatement was compounded into the high end IPCC AR4 WG2 estimated extinction risk for all animal species.
As two further examples of selection bias from Thomas et. al. plants, the World Wildlife Federation estimates there are 80,000 plant species in the Amazon region (nobody really knows). Thomas et. al. selected 9 (but did not say which 0.01%), and modeled a 69-87% extinction risk for those. Those estimates became part of the simple plant averages for all 4 regions. Thomas et. al. selected 243 out of roughly 400 species of South African Proteaceae (afrikanns ‘suikerbossie’ or sugarbushes, of which there are 80 generi and roughly 1600 species worldwide including the familiar macadamia nut). South African Proteaceae grow mainly in a specialized Cape Hope ecosystem known as the Fynbos, which covers just 6.7% of South Africa. The Queensland EBA ‘trick’ was also applied to plants.
IPCC AR4 WG2 relied on nothing but one multiply flawed paper for its oft-repeated extinction estimates.[xi] That is a gross error equivalent to the AR4 Himalayan glaciers fiasco. Except better hidden, so undiscovered until now.
It originally appeared from leaked draft documents that IPCC AR5 WG2 was going to do an extinction prediction climb down.[xii] That ultimately did not happen in the final SPM released 3/31/2014 (the following is from SPM B-2):
“A large fraction of both terrestrial and freshwater species faces increased extinction risk under projected climate change during and beyond the 21st century, especially as climate change interacts with other stressors, such as habitat modification, over-exploitation, pollution, and invasive species (high confidence).”
The assertion remains, but now without falsifiable quantification. At least the actual causes of species extinction risk are now also noted as ‘interactions’.
WG2 Technical summary (TS) incorrectly summarized 4.3.2.5 (below):
“While recent warming contributed to the extinction of many species of Central American amphibians (medium confidence), most recent observed terrestrial-species extinctions have not been attributed to recent climate change, despite some speculative efforts [white possum?] (high confidence).”
The correct number of CAGW mediated amphibian extinctions is exactly zero. The USGS [xiii], Amphibiaweb [xiv], and all recent scientific literature [xv] say the global amphibian decline since about 1980 is driven by the spread of chtryidiomycosis infection, which also did in the famous golden toad. [xvi] It is, to borrow from the present vernacular, EBOLA for amphibians.
AR5 WG2 Emergent Risks and Key Vulnerabilities §19.5.1 doubled down on AR4 by predicting more extinctions from warming at an implausible 4°C.[xvii]
“Assessments of ecological impacts at and above 4°C warming imply a high risk of extensive loss of biodiversity with concomitant loss of ecosystem services. AR4 estimated that 20-30% of species were likely at increasingly high risk of extinction as global mean temperatures exceed a warming of 2-3°C above pre-industrial levels; hence 4°C warming implies further increases to extinction risks for an even larger fraction of species. However, there is low agreement on the numerical assessment since as more realistic details have been considered in models, it has been shown that extinction risks may be either under- or overestimated when using the simpler models.”
And despite this low agreement, the SPM still asserted high confidence—once habitat loss, over-exploitation, pollution, and invasive species were added in.
Only when delving into the lengthy Chapter 4 scientific details of the actual extinction risks meta-analysis by true ecologists and biologists is a more realistic and nuanced perspective revealed. It is not reflected in the SPM, the TS, or chapter 19. To summarize the scientific findings of WG2 4.3.2.5 (well worth a separate if somewhat long read for those interested in learning ecology):
-Observed global extinctions over the past few centuries have been caused by habitat loss, overexploitation, pollution, and invasive species.
-Climate change has been identified as one of the extinction drivers only in amphibians, most notably the Golden Toad of Monteverde. This raised important issues about attribution: (1) an extremely virulent invasive fungal infection and (2) changes in regional climate related to natural variation.
-The paleontological record indicating low extinction rates over the past few hundred thousand years of substantial natural fluctuations in climate raises concerns that modeled forecasts of high extinction rates due entirely to climate change may be overestimated.
- There is growing consensus that it is the interaction of climate change with existing global pressures that poses the greatest threat to species.
- There is low agreement on the overall number of species, taxa, regions, and time frames that might be at risk mainly from climate change, and a high degree of uncertainty from phenotype plasticity, fine scale climatic variation, and confounding existing extinction causes that continue to grow.
Yet the AR5 WG2 SPM persisted in pronouncing large climate extinction risk. Chapter 4 did not correct the AR4 overestimate that CAGW commits 21-52% of all species to extinction by 2100 despite multiple subsequent peer-reviewed criticisms of the deeply flawed single paper on which it was ultimately based. Doing so would have exposed the biased AR4 process for what it was.
A very poor semi-disguised selection biased meta-analysis on top of a single grossly but ‘hidden’ selection biased paper itself using repudiated methods.
References and endnotes:
[i] Lyver et. al., Trends in Breeding Populations of Adélie penguins…, PLOS|one 9: e91188 (2014)
[ii] Lynch and LaRue, First Global Census of the Adelie Penguin, The Auk 131: 457-466 (2014)
[iii] Anchukaitis and Evans, Tropical cloud forest climate variability and the demise of the Monteverde golden toad, PNAS: 0908572107 (2010)
[iv] Rumours of Possums Death were greatly exaggerated, New Scientist 3/31/2009
[v] Botkin et. al., Forecasting the effects of global warming on biodiversity, Bioscience 57: 227-236 (2007)
[vi] Thomas et. al., Extinction Risk from Climate Change, Nature 427: 145-148 (2004)
[vii] The fish estimate was 4-22% in just 66 out of 165 rivers (AR4 WG2 table 4.1 #53 used >10%) from a single paper Xenopoulos et. al., Scenarios of freshwater fish extinction from climate change and water withdrawal, Global Change Biology 11: 1557-1564 (2005). This paper took IPCC AR4 drought predictions, modeled additional irrigation water withdrawals, and then modeled fish extinctions as river flows declined. In 99 out of 165 rivers there were none. IPCC ignored the important detail that in 60% of studied rivers there was no extinction risk at all, rather extrapolating a modeled midpoint for the 40% to all freshwater fish globally
[viii] Brooks et. al., Deforestation predicts the number of threatened birds in insular Southeast Asia, Conserv. Biol. 11: 382-394 (1997) and Deforestation and Bird Extinction in tropical forest fragments, Conserv. Biol. 13: 1140-1150 (1999)
[ix] He and Hubbell, Species-area relationships always overstate extinction risk from habitat loss, Nature 473: 368-371 (2011)
[x] Pielke and Wilby, Regional Climate Downscaling: whats the point?, EOS 93: 52-53 (2012)
[xi] For example, at the Nature Conservancy and EPA websites.
[xii] Bojanowski, Will global warming really trigger mass extinctions?, Der Spiegel 3/24/2014 (translated from German)
[xiii] USGS factsheet 2012-3092
[xiv] amphibiaweb.org, maintained by the University of California Berkeley.
[xv] E.g. Lips et. al. Emerging infectious disease and the loss of biodiversity in a neotropical amphibian community, PNAS 103: 3165-3170 (2006)
[xvi] Yet in another ironic twist to the extinction story, Pounds, who in 1999 declared the golden toad to be the very first victim of CAGW, published a 2006 paper saying Central American chytridiomycosis was exacerbated by moderating climate, and kept in check by climate extremes. Pounds, et. al., Widespread amphibian extinctions from epidemic disease spread by global warming, Nature 439: 161-167 (2006)
[xvii] Lead authors are former Chief Scientist for the Environmental Defense Fund Michael Oppenheimer and Tyndall Centre’s climate impact simulation modeling head Rachel Warren.
JC note: This is a guest post, please keep your comments relevant and civil. For reference, Rud’s previous CE posts can be found [here].Filed under: Climate change impacts
