Enviro Valley: Print Email Facebook Twitter More Global warming rate could be less than feared

High levels of carbon dioxide in the atmosphere may have less of an impact on the rate of global warming than feared, a new study suggests.

The authors of the study stress that global warming is real and that increases in atmospheric CO2, which has doubled from pre-industrial standards, will have multiple serious impacts.
But more severe estimates that predict temperatures could rise up to an average of 10 degrees Celsius are unlikely, the researchers report in the journal Science.
The 2007 United Nations Intergovernmental Panel on Climate Change (IPCC) report estimates that surface temperatures could rise by as much as an average of 3 degrees with a doubling of atmospheric CO2 from pre-industrial standards.
The new study suggests temperatures will rise on average 2.3 degrees under the same conditions.
"When you reconstruct sea and land surface temperatures from the peak of the last ice age 21,000 years ago - which is referred to as the Last Glacial Maximum - and compare it with climate model simulations of that period, you get a much different picture," said lead author Andreas Schmittner, from Oregon State University.
"If these palaeoclimatic constraints apply to the future, as predicted by our model, the results imply less probability of extreme climatic change than previously thought."
Scientists have long struggled to quantify climate sensitivity, or how the Earth will respond to projected increases in carbon dioxide, the main greenhouse gas.

Global scale

Associate Professor Schmittner notes that many previous studies only looked at periods spanning from 1850 to today, thus not taking into account a fully integrated palaeoclimate data on a global scale.
The researchers based their study on ice age land and ocean surface temperature obtained by examining ices cores, bore holes, seafloor sediments and other factors.
When they first looked at the palaeoclimatic data, the researchers only found very small differences in ocean temperatures then compared to now.
"Yet the planet was completely different - huge ice sheets over North America and northern Europe, more sea ice and snow, different vegetation, lower sea levels and more dust in the air," Associate Professor Schmittner said.
"It shows that even very small changes in the ocean's surface temperature can have an enormous impact elsewhere, particularly over land areas at mid to high latitudes."
He warned that continued, unabated use of fossil fuels could lead to similar warming of sea surfaces today.

Solid foundation

Professor Colin Prentice from Macquarie University says he is not surprised by the results.
Professor Prentice, who was not involved in the study, says the new paper is based on a careful compilation of data and addresses an issue that is "absolutely central".
"What it means is we can be a bit more sure about the sort of range of temperature changes that will result from the given change in the amount of fossil fuel and CO2 and other greenhouse gases," he said.
"The key point is that there has been ongoing buzz about the possibility that the climate sensitivity may be way, way higher than in mainstream climate models.
"So for very technical reasons with data just from contemporary observations and observations from the recent historical period, you just haven't got enough information to really rule out those numbers.
"What [this study] has shown is that those very high values are ruled out.
"So it means we still have a major issue about climate change, but it is much better quantified, much better pinned down."
The study was funded by the National Science Foundation.

Source: http://www.abc.net.au/news/2011-11-25/global-warming-rate-could-be-less-than-feared/3694896

The winters of 2009-10 and 2010-11 were marked extremes, a recent study from the American Geophysical Union reports. We mostly heard of the cold. More defining, but apparently not as newsworthy, our planet experienced many extreme warm spells in recent winters. The recent research examined daily wintertime temperature extremes since 1948. It also found that “warm extremes were much more severe and widespread than the cold extremes during the northern hemisphere winters of 2009-10 (which featured an extreme snowfall episode on the East Coast dubbed “snowmaggedon”) and 2010-11.”
Natural Climate variation due to North Atlantic Oscillation (NAO) explains cyclical cold spells. However,…
the long-term extreme warmth trend was left unexplained,… or, rather, just as one would expect in a period of accelerating global warming.
Kristen Guirguis explains:
“We investigated the relationships between prominent natural climate modes and extreme temperatures, both warm and cold. Natural climate variability explained the cold extremes; the observed warmth was consistent with a long-term warming trend.” As Guirguss is a postdoctoral researcher at the Scripps Institution of Oceanography at UC-San Diego and lead author of the study, which is set to be published in the journal Geophysical Research Letters (a publication of the American Geophysical Union), is telling us this, one must stop to consider this as a well-informed, accurate recent analysis of our planet and it’s patterns.
But, to clarify, here’s more from a piece on Climates Progress, “Last Two Winters’ Warm Extremes More Severe Than Their Cold Snaps, Study Finds, from Scripps climate researcher Alexander Gershunov, a report co-author: “Over the last couple of years, natural variability seemed to produce the cold extremes, while the warm extremes kept trending just as one would expect in a period of accelerating global warming.”