The risk posed to mankind and the environment by even small changes in average global temperatures is much higher than believed even a few years ago, a study said on Monday.
The Earth will not have to warm up as much as had been thought to cause serious consequences, including more extreme weather and increasing threats to plants and animals, the scientists report in this week’s online edition of Proceedings of the National Academy of Science.
The Intergovernmental Panel on Climate Change (IPCC) estimated that the risk of increased severe weather would rise with a global average temperature increase of between 1˚C and 2˚C above 1990 levels. The US National Climatic Data Center currently reports that global temperatures have risen 0.12˚ since 1990.
Now, researchers report that “increases in drought, heat waves, and floods are projected in many regions and would have adverse impacts, including increased water stress, wildfire frequency, and flood risks starting at less than 1 degree of additional warming above 1990 levels.”
Indeed, “it is now more likely than not that human activity has contributed to observed increases in heat waves, intense precipitation events, and the intensity of tropical cyclones,” concluded the researchers led by Joel Smith of Stratus Consulting.
The study updated a 2001 IPCC assessment that looked at temperature changes and the risks they pose.
“Today, we have to assume that the risks of negative impacts of climate change on humans and nature are larger than just a few years ago,” said Hans-Martin Fussel, one of the authors of the report.
The new study found that even small changes of global mean temperatures could produce the kinds of conditions singled out as “reasons for concern” in the 2001 study.
Those included risks to threatened systems such as coral reefs or endangered species; and extreme weather events like cyclones, heat waves or droughts.
Other “reasons for concern” involved the way the impact of climate change is distributed, the aggregate damage caused and the risk of “large scale discontinuities” such as the deglaciation of the Greenland ice sheets.
“Compared with results reported in the [2001 assessment], smaller increases in GMT [global mean temperatures] are now estimated to lead to significant or substantial consequences in the framework of the five ‘reasons for concern,’” the study said.
The report said its conclusions were based on observations of impacts already occurring because of global warming and better understanding of the risks associated with rising mean temperatures. They also were based on “growing evidence that even modest increases in GMT above levels circa 1990 could commit the climate system to the risk of very large impacts on multiple century time scales,” the study said.
“If the associated risks are larger, the necessity is also larger to reduce the greenhouse gases emissions and to support affected regions to cope with the unavoidable consequences of climate change,” Fussel said in a statement.
The new study says there is new evidence of greater vulnerability to climate change for specific populations, such as the poor and elderly, in not only developing but also developed countries.
“Events such as Hurricane Katrina and the 2003 European heat wave have shown that the capacity to adapt to climate-related extreme events is lower than expected and, as a result, their consequences and associated vulnerabilities are higher than previously thought,” the scientists report.