- Banned
- #201
What if global warming isn't as severe as predicted?
By Rebecca Lindsey
August 3, 2010
The Intergovernmental Panel on Climate Change stated in their most recent report that global surface temperature at the end of this century will probably be between 1.8 and 4 degrees Celsius warmer than it was at the end of the last century.
Its natural to question whether we and future generations will regret our efforts to reduce greenhouse gas emissions if it turns out global warming isnt as bad as predicted. But the best science we have to guide us at this time indicates that the chance that warming will be much larger than the best estimate is greater than the Chan that it will be much smaller.
Climate scientists know that there is plenty they dont know about the way the Earth system works. Some of the physical processes that models describe are thoroughly well-establishedthe melting point of ice, for example, and the law of gravity.
Other physical processes are less perfectly known: when the air temperature is not far below 0 Celsius, for example, will water vapor condense into liquid or ice? Either is possible, depending on atmospheric conditions.
To understand how uncertainty about the underlying physics of the climate system affects climate predictions, scientists have a common test: they have a model predict what the average surface temperature would be if carbon dioxide concentrations were to double pre-industrial levels.
They run this simulation thousands of times, each time changing the starting assumptions of one or more processes. When they put all the predictions from these thousands of simulations onto a single graph, what they get is a picture of the most likely outcomes and the least likely outcomes.
The pattern that emerges from these types of tests is interesting. Few of the simulations result in less than 2 degrees of warmingnear the low end of the IPCC estimatesbut some result in significantly more than the 4 degrees at the high end of the IPCC estimates.
This pattern (statisticians call it a right-skewed distribution) suggests that if carbon dioxide concentrations double, the probability of very large increases in temperature is greater than the probability of very small increases.
Our ability to predict the future climate is far from certain, but this type of research suggests that the question of whether global warming will turn out to be less severe than scientists think may be less relevant than whether it may be far worse.
Graph of results http://earthobservatory.nasa.gov/blo...-as-predicted/
Climate sensitivity estimates have been falling like a rock recently. The IPCC has already had to print a correction to the AR4 report on them. Many of the models still assume the larger estimates and it shows in their incorrect projections.
You must be way ahead of the Internet.
The only reported AR4 update that the Internet knows about says this.
"This report provides an update of the IPCC Fourth Assessment Report (AR4), focusing on the physical climate system that in the IPCC work is addressed by its Working Group I. The report considers progress in understanding of the human and natural drivers of climate change, climate observations, attribution, key climate feedback, as well as ocean acidification. Recent developments and near future prospects of climate modelling are also discussed in brief. Some of the key findings that the recent literature brings forth include:"
"Parts of the Greenland and Antarctic ice sheets have shown rapid melt over recent years."
"Solar cycle effects on global temperatures are small compared to anthropogenic forcing"
"More emerging research on the "other CO2 problem", ocean acidification
Climate change may have significant effects on natural carbon sinks"
"The report is written by four leading Nordic climate scientists: Markku Rummukainen, Jouni Räisänen, Jens Hesselbjerg Christensen and Halldór Björnsson on behalf of the Nordic ad hoc Group on Global Climate Negotiations. The Nordic ad hoc Group on Global Climate Negotiations prepares reports and studies, conducts meetings and organises conferences to support the Nordic negotiators in the UN climate negotiations. The overall aim of the group is to contribute to a global and comprehensive agreement on climate change with ambitious emission reduction commitments."
As IPCC is working on AR5 due out next year, who is updating AR4?