Global warming: Record heat of today could be new norm in 2047, study says
A new study suggests that, globally, the maximum temperatures of the past 150 years will be the new minimum by 2047. It also pinpoints when this shift will take place in 26 cities.
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Mora's team notes that widespread adverse effects from the shift are likely to appear earliest in the tropics because marine and terrestrial plants and animals there have adapted to a climate with relatively with small shifts in extremes.Skip to next paragraph
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The team based its study on 39 climate models the IPCC used for its latest climate-assessment reports and used climate records from 1860 to 2005 to determine historical ranges of natural variability.
While the researchers express the changes in terms of temperatures near the surface, they also examined precipitation, evaporation, the movement of water through plants, heat transferred from Earth's surface to the atmosphere, as well as ocean acidity. The researchers found that with the exception of ocean acidification, whose variability already falls outside of historic bounds, these other actors in the climate system will shift to new minimums that exceed past maximums somewhat later than near-surface temperatures.
The study Mora's team has produced "goes a long way toward pinning down the time line," notes Kevin Trenberth, a researcher at the National Center for Atmospheric Research in Boulder, Colo., who was not a member of Mora's team but whose research focuses on climate change and climate variability.
But the conclusions about the tropics may be suspect, he says in an e-mail. The main source of variability in the tropics is the swing between El Niño and La Niña. These involve shifts in warm sea-surface temperatures and air-pressure patterns in the tropical Pacific that seesaw from east to west and back every two to seven years. The team showed no evidence of evaluating how well the models replicate the frequency and intensity of these important climate swings.
Some models overstate the intensity of the climatological siblings, known collectively as the El Niño-Southern Oscillation (ENSO), while others produce no ENSO at all.
And since water resources represent a critical element for ecosystems and societies, "one would like to know a lot more about monsoons" and other seasonal changes in precipitation in the tropics.
For his part, Mr. Lowenstein says he suspects the team's results are too conservative. It bases its timing estimates on the year after which all succeeding years display the new climate regime. But, says Lowenstein, a looming shift in climate regimes can have a significant effect on people and ecosystems even if the new range of variability occurs in five years out of 11, instead of 11 out of 11.
Still, he and other researchers say the study provides useful insights into the projected patterns, timing, and effects of a new climate regime and the importance of putting a serious brake on emissions while helping the countries earliest hit and least able to cope adapt to the coming changes.