Human link to climate change stronger than ever: draft report

LONDON Fri Dec 14, 2012 11:20am EST

LONDON (Reuters) - International climate scientists are more certain than ever that humans are responsible for global warming, rising sea levels and extreme weather events, according to a leaked draft report by an influential panel of experts.

The early draft, which is still subject to change before a final version is released in late 2013, showed that a rise in global average temperatures since pre-industrial times was set to exceed 2 degrees Celsius by 2100, and may reach 4.8 Celsius.

"It is extremely likely that human activities have caused more than half of the observed increase in global average surface temperatures since the 1950s," the Intergovernmental Panel on Climate Change (IPCC) draft report said.

"Extremely likely" in the IPCC's language means a level of certainty of at least 95 percent. The next level is "virtually certain", or 99 percent, the greatest possible certainty for the scientists.

The IPCC's previous report, in 2007, said it was at least 90 percent certain that human activities, led by burning fossil fuels, were the cause of rising temperatures.

The draft was shown on a climate change skeptic blog.

The IPCC said the unauthorized, premature posting of the draft may lead to confusion because the report was still work in progress and was likely to change before it is released.

A United Nations conference last week aimed at curbing emissions of greenhouse gases blamed for global warning yielded no progress and three countries - Canada, Russia and Japan - have abandoned the Kyoto Protocol limiting the emissions.

The United States never ratified it in the first place, and it excludes developing countries where emissions are growing most quickly.

Countries agreed to extend Kyoto to 2020, but only those covering less than 15 percent of world greenhouse gas emissions signed up. Developing nations said they would push next year for a radical U.N. mechanism to compensate them for the impact of climate change.

The IPCC said it had "high confidence" that human activity had caused large-scale changes in oceans, in ice sheets or mountain glaciers, and in sea levels in the second half of the twentieth century, according to the draft.

It said some extreme weather events had also changed due to human influences.


The draft's scenarios forecast a rise in temperatures of between 0.2 and 4.8 Celsius this century - a narrower band than in 2007. But in almost all of the scenarios, the rise would exceed 2 degrees Celsius.

Governments pledged in 2010 to try to stop global temperatures rising by more than 2 degrees, a threshold seen by scientists as the maximum to avoid more extreme weather, droughts, floods, and other climate change impacts.

Carbon dioxide concentrations in the atmosphere were the highest in 800,000 years, according to the draft report.

The draft also said that sea levels were likely to rise by between 29 and 82 centimeters by the end of the century - compared to 18-59 centimeters projected in the 2007 report.

Rising sea levels are a threat to people living in low-lying areas, from Bangladesh to the cities of New York, London and Buenos Aires. They open up the risk of storm surges, coastal erosion and, in the worst case scenario, the complete swamping of large areas of land.

The IPCC carries weight because it brings together all scientific research on climate change and informs policymakers.

Many countries want to study the final IPCC report before signing up to a new global pact to cut greenhouse gas emissions.

The draft included a possible future acceleration of ice loss from Antarctica and Greenland, which was omitted in 2007. It stopped short of including some research carried out since 2007 that suggested seas may rise by up to 2 meters by 2100.

(Editing by Tom Pfeiffer)

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Comments (2)
gregbrew56 wrote:
Let the denying begin…

Dec 14, 2012 4:38pm EST  --  Report as abuse
jrwondra wrote:
Of course, the authors merely parrot the Executive Summary, which does not, actually, lead to the Headline conclusion; although that is clearly the impression they (and the IPCC) wish to convey.

If one were to actually READ the leaked Chapters, one would find that the draft AR5 significantly departs from the AR4 premise that man must be the sole/major cause of climate warming, since it can’t be attributed to Total Solar Irradiance.
In fact, the Chapter 7 authors specifically state:
“The forcing from changes in total solar irradiance alone does not seem to account for these observations, implying the existence of an amplifying mechanism such as the hypothesized GCR-cloud link. ”
(page 7-43, lines 1-5)

The primary leaker, Alec Rawls, explains:
“The Chapter 7 authors are admitting strong evidence (“many empirical relationships”) for enhanced solar forcing (forcing beyond total solar irradiance, or TSI), even if they don’t know what the mechanism is.
The AR4 analysis, where post-1980 warming gets attributed to the human release of CO2 on the grounds that it cannot be attributed to solar irradiance, cannot stand in the face of the Chapter 7 admission of substantial evidence for solar forcing beyond solar irradiance. Once the evidence for enhanced solar forcing is taken into account we can have no confidence that natural forcing is small compared to anthropogenic forcing.
[T]he Chapter 7 team is now being explicit about what this evidence means: that some mechanism of enhanced solar forcing must be at work.
The admission of strong evidence for enhanced solar forcing changes everything. The climate alarmists can’t continue to claim that warming was almost entirely due to human activity over a period when solar warming effects, now acknowledged to be important, were at a maximum.”

Let the Alarmists deny!

Dec 15, 2012 5:26pm EST  --  Report as abuse
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