Working Group 2 of the Intergovernmental Panel on Climate Change recently released the final version of its contribution to the IPCC Fifth Assessment Report: Climate Change 2014: Impacts, Adaptation, and Vulnerability. The WG2 report contains 1,731 pages of text, figures, boxes, footnotes and references, the first 832 of which list every negative impact climate change is having or could conceivably have on the Earth, its physical state, its ecosystems and the people who populate it. I doubt that anyone has ever read it from beginning to end. I certainly haven’t.
But the report’s mind-numbing length hasn’t stopped people from interpreting it the way they think it should be interpreted. And because no one bothered to read the fine print everyone thinks the IPCC is saying that the adverse impacts of human-caused climate change are already being felt:
Rising sea levels threaten every coastline. More powerful storms and floods threaten every continent. More frequent drought and crop failures breed hunger and conflict in places where hunger and conflict already thrive. On shrinking islands, families are already being forced to flee their homes as climate refugees. (Barack Obama)
Climate change is already having sweeping effects on every continent and throughout the world’s oceans … ice caps are melting, sea ice in the Arctic is collapsing, water supplies are coming under stress, heat waves and heavy rains are intensifying, coral reefs are dying, and fish and many other creatures are migrating toward the poles or in some cases going extinct.(New York Times)
The record rainfall and storm surges that have brought flooding across the UK are a clear sign that we are already experiencing the impacts of climate change. (Guardian)
But that isn’t what the IPCC is saying. A single sentence on page 4 of the Summary for Policymakers puts the IPCC’s conclusions in a different perspective:
Attribution of observed impacts in the WGII AR5 generally links responses of natural and human systems to observed climate change, regardless of its cause.
That’s right. Regardless of its cause. Working Group 2 isn’t claiming that these observed impacts are necessarily a result of human activities. They could equally well be the result of natural climate change – the IPCC makes no distinction. And if they are, then President Obama, the New York Times, the Guardian and all the others who believe that the adverse impacts of human-caused climate change are already being felt have got it wrong.
The key question here is clearly what fraction of the observed impacts of climate change that the IPCC identifies is human-caused and how much natural. Let’s see if we can put some probabilities on this.
The Working Group 2 report highlights nine specific claims regarding the physical impacts of climate change in Section A-1 of the Summary for Policymakers (I increased the number to ten by dividing one claim into two.) Three are non-specific, irrelevant or unintelligible and are not discussed:
In recent decades, changes in climate have caused impacts on natural and human systems on all continents and across the oceans.
Differences in vulnerability and exposure arise from non-climatic factors and from multidimensional inequalities often produced by uneven development processes. These differences shape differential risks from climate change.
Climate-related hazards exacerbate other stressors, often with negative outcomes for livelihoods, especially for people living in poverty.
The remaining seven are discussed below in order of appearance (note that I’ve removed superfluous wording in some cases in the interests of brevity):
Claim 1: Glaciers continue to shrink almost worldwide due to climate change.
Evaluation: The world’s glaciers are unquestionably shrinking overall because of climate change. But is the climate change anthropogenic? One way of checking is to compare glacier behavior with an anthropogenic climate change metric to see whether the two coincide, which they should if one caused the other. Such a comparison is shown on the graphic below, which plots the Oerlemans estimates of global glacier length change since 1700 with the GISS estimates of net anthropogenic radiative forcings since 1880 (earlier values can be assumed to be close to zero if not exactly zero):
Oerlemans glacier shrinkage vs. GISS anthropogenic forcings
And the timing doesn’t match. According to Oerlemans the world’s glaciers began to shrink in the early 1800s but according to GISS anthropogenic forcings didn’t become significant until after 1950 (the ~0.2 watts/sq m of forcing in 1950 would have generated only about 0.1C of warming). Oerlemans’ results also show no sign of acceleration in the shrinkage rate after 1960.
These results imply that something other than human interference initiated the glacier shrinkage and that human interference didn’t make any detectable difference when it finally did become significant. (Glaciologists acknowledge that human activities are not the only contributor to glacier shrinkage, as the following quote from Nature attests: “The widespread idea that glacier retreat is the sole consequence of increased air temperature is overly simplistic. Glaciologists have known for more than 50 years that glaciers are sensitive to a variety of climate variables, not all of which can be attributed to global warming.”)
Conclusion: There is good evidence to suggest that much if not substantially all of the glacier shrinkage over the last 200 years was a result of natural climate change.
(Note: Section A-1, curiously, does not mention either sea level rise or Arctic sea ice retreat. However, the Jevrejeva et al. sea level reconstruction closely tracks the Oerlemans glacier plot with the Y-scale inverted, so the above comments would also apply to sea level rise. The recent retreat of Arctic sea ice is another case where climate change was undoubtedly the cause, but whether the climate change was anthropogenic is again open to question, and the ice lost in the Arctic was largely offset globally by ice gained in the Antarctic anyway.)
Claim 2: Many terrestrial, freshwater, and marine species have shifted their geographic ranges ….. in response to ongoing climate change. See Figure SPM.2B
Evaluation: Here is Figure SPM.2B:
Figure SPM.2B: Average rates of change in distribution (km per decade) for marine taxonomic groups based on observations over 1900–2010. Positive distribution changes are consistent with warming (moving into previously cooler waters, generally poleward). The number of responses analyzed is given within parentheses for each category.
Multiplying the distribution change rates by the 11-decade 1900-2010 interval of measurement gives total shifts of a few hundred kilometers for most taxa but over 1,000 km for zooplankton and around 5,000 km for phytoplankton. If this latter estimate is correct then the phytoplankton that now inhabit the temperate and sub-polar oceans must have migrated there from the tropical oceans over the course of the last 100 or so years, surviving a 15-20C water temperature decrease on the way.
Conclusion: The observations are suspect.
Claim 3: While only a few recent species extinctions have been attributed as yet to climate change, natural global climate change at rates slower than current anthropogenic climate change caused significant ecosystem shifts and species extinctions during the past millions of years.
Evaluation: None of the species extinction attributions stands up to scrutiny. There is still no proven instance of a species extinction caused by anthropogenic climate change. Section 188.8.131.52.5. of the WG2 report, “Observed global extinctions”, acknowledges this:
Most extinctions over the last several centuries have been attributed to habitat loss, overexploitation, pollution, or invasive species, and these are the most important current drivers of extinctions. Of the more than 800 global extinctions documented by the International Union for Conservation of Nature only 20 have been tenuously linked to recent climate change.
Buried somewhere in the text of the report there may be evidence to support the claim that extinctions millions of years ago occurred when the climate was changing more slowly than it is now, but paleotemperature records that go back this far don’t provide enough detail to tell us how rapidly the global climate was changing on the century-scale, and paleotemperature records that go back thousands of years, such as the GISP2 ice core record, suggest that climate was changing at least as fast as it is now in the late Pleistocene:
Rapid late Pleistocene temperature changes in the GISP2 record
Conclusion: Climate change, human-caused or natural, fast or slow, has so far caused zero species extinctions.
Claim 4: Based on many studies covering a wide range of regions and crops, negative impacts of climate change on crop yields have been more common than positive impacts. See Figure SPM.2C.
Evaluation: Here is Figure SPM.2C:
Figure SPM.2C: Summary of estimated impacts of observed climate changes on yields over 1960–2013 for four major crops in temperate and tropical regions, with the number of data points analyzed given within parentheses for each category.
And here is actual world grain production over the 50-year period when human-caused climate change was allegedly cutting crop yields by up to two percent a decade:
Conclusion: Any overall negative impact that climate change, human-caused or natural, might be having on crop yields is being swamped by positive impacts from other factors, one of which is presumably higher atmospheric CO2.
Claim 5: Impacts from recent climate-related extremes, such as heat waves, droughts, floods, cyclones, and wildfires, reveal significant vulnerability and exposure of some ecosystems and many human systems to current climate variability.
Evaluation: This statement implies that climate change has increased the severity and frequency of extreme weather events but doesn’t overtly claim that it has, which is good because the Working Group 1 report concluded that it hasn’t. According to this summary of key statements on extreme weather events compiled by Roger Pielke Jr. WG1 in fact failed to identify robust trends in any extreme weather events:
• “Overall, the most robust global changes in climate extremes are seen in measures of daily temperature, including to some extent, heat waves. Precipitation extremes also appear to be increasing, but there is large spatial variability”
• “There is limited evidence of changes in extremes associated with other climate variables since the mid-20th century”
• “Current datasets indicate no significant observed trends in global tropical cyclone frequency over the past century … No robust trends in annual numbers of tropical storms, hurricanes and major hurricanes counts have been identified over the past 100 years in the North Atlantic basin”
• “In summary, there continues to be a lack of evidence and thus low confidence regarding the sign of trend in the magnitude and/or frequency of floods on a global scale”
• “In summary, there is low confidence in observed trends in small-scale severe weather phenomena such as hail and thunderstorms because of historical data inhomogeneities and inadequacies in monitoring systems”
• “In summary, the current assessment concludes that there is not enough evidence at present to suggest more than low confidence in a global-scale observed trend in drought or dryness (lack of rainfall) since the middle of the 20th century due to lack of direct observations, geographical inconsistencies in the trends, and dependencies of inferred trends on the index choice. Based on updated studies, AR4 conclusions regarding global increasing trends in drought since the 1970s were probably overstated. However, it is likely that the frequency and intensity of drought has increased in the Mediterranean and West Africa and decreased in central North America and north-west Australia since 1950”
• “In summary, confidence in large scale changes in the intensity of extreme extratropical cyclones since 1900 is low”
Conclusion: Climate change, human-caused or natural, has to date caused no significant increases in the intensity or frequency of extreme weather events.
Claim 6: At present the worldwide burden of human ill-health from climate change is relatively small … and is not well quantified. However, there has been increased heat-related mortality and decreased cold-related mortality in some regions as a result of warming.
Evaluation: The World Health Organization publishes occasional reports purporting to demonstrate that climate change is killing/will kill hundreds of thousands of people each year, but the WG2 report correctly describes these and other similar studies as “not well quantified”. On the question of climate change causing increased heat-related mortality and decreased cold-related mortality it’s generally accepted that cold kills more people than heat, so:
Conclusion: Global warming is good for you.
Claim 7: Violent conflict increases vulnerability to climate change.
Evaluation: Violent conflict increases vulnerability to everything.
Conclusion: Quoted from Section 12.5 of the WG2: “Several studies examine the relationship between short-term warming and armed conflict. Some of these find a weak relationship, some find no relationship, and collectively the research does not conclude that there is a strong positive relationship between warming and armed conflict.”
That completes the review of the claims listed in section A-1 of the Summary for Policymakers. The report does, however, briefly discuss ocean acidification on page 47 of the Technical Summary, concluding as follows:
Few field observations to date demonstrate biological responses attributable to anthropogenic ocean acidification.
And that concludes the investigation. There is no good evidence linking human activities to any of the observed impacts of climate change listed in the Summary for Policymakers of the WG2 report.
Obama et al. indeed seem to have got it wrong.
By Roger Andrews
Source – www.euanmearns.com
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