When it comes to climate change, the writing is on the wall.
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When it comes to climate science, the writing is on the wall.

Climate hawks are buzzing over leaks from the fifth big climate report of the Intergovernmental Panel on Climate Change, due to be officially released in September. Spoiler: Scientists are pretty damn confident that we’re screwing up the climate.

An earlier draft was leaked in December by climate deniers trying to undermine the case for anthropogenic climate change. News of more recent leaked drafts comes to us from Reuters, which has no such agenda. Reuters sums up the report this way:

Climate scientists are surer than ever that human activity is causing global warming, according to leaked drafts of a major U.N. report, but they are finding it harder than expected to predict the impact in specific regions in coming decades. …

Drafts seen by Reuters of the study by the U.N. panel of experts, due to be published next month, say it is at least 95 percent likely that human activities — chiefly the burning of fossil fuels — are the main cause of warming since the 1950s.

That is up from at least 90 percent in the last report in 2007, 66 percent in 2001, and just over 50 in 1995, steadily squeezing out the arguments by a small minority of scientists that natural variations in the climate might be to blame. …

Experts say that the big advance in the report, due for a final edit by governments and scientists in Stockholm from Sept. 23-26, is simply greater confidence about the science of global warming, rather than revolutionary new findings.

Joe Romm at Climate Progress reminds us that the IPCC reports are generally conservative:

[The forthcoming report] is just a (partial) review of the scientific literature … [L]ike every IPCC report, it is an instantly out-of-date snapshot that lowballs future warming because it continues to ignore large parts of the recent literature and omit what it can’t model. For instance, we have known for years that perhaps the single most important carbon-cycle feedback is the thawing of the northern permafrost. The IPCC’s Fifth Assessment climate models completely ignore it, thereby lowballing likely warming this century.

Here’s reaction from climate scientist Michael Mann, via Climate Progress:

The report is simply an exclamation mark on what we already knew: Climate change is real and it continues unabated, the primary cause is fossil fuel burning, and if we don’t do something to reduce carbon emissions we can expect far more dangerous and potentially irreversible impacts on us and our environment in the decades to come.

And, for entertainment value, here’s reaction from denier-ville, via the Hockey Schtick blog:

[A]ll of these fatuous figures [about likelihood of human causation] are pulled out of the air to support the IPCC ideologies and not based upon any statistical analysis or science.

Back in reality-ville, John Abraham at The Guardian thanks all the climate scientists who have donated time to produce the IPCC report and wonders whether we need them to keep spending their time this way:

[T]he IPCC has done its job. For this fifth report, they have synthesized the science and provided enough evidence that action is warranted. How many more reports of this type do we need? Will a sixth report that confirms what we already know make much of a difference? Will a seventh? …

Whatever the future holds for the IPCC, the history books will tell us we were warned. Time and time again, the world’s best scientists have sent us clear messages.