Temperature change over past 11,300 years (in blue, via Science, 2013) plus projected warming over the next century on humanity’s current emissions path (in red, via recent literature, much of which is reviewed in the new IPCC report.)
The Fifth — and hopefully final — Assessment Report (AR5) from the UN Intergovernmental Panel On Climate Change (IPCC) is due next month. The leaks are already here:
Drafts seen by Reuters of the study by the UN 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.
This is a doubly impressive story since, as we’ve reported, Reuters has slashed climate coverage and pressured reporters to include false balance. Leading climatologists who have seen drafts of the report confirm this story’s accuracy.
Of course, nothing in the report should be a surprise to readers of Climate Progress, since the AR5 is just a (partial) review of the scientific literature (see my 12/11 post, It’s “Extremely Likely That at Least 74% of Observed Warming Since 1950″ Was Manmade; It’s Highly Likely All of It Was). The draft AR5 confirms that natural forces played a very small role in warming since 1950, which again means that human activity is highly likely be a source of virtually all of the recent warming.
I say the AR5 is a “partial” review that is “hopefully” the last because, like every IPCC report, it is an instantly out-of-date snapshot that lowballs future warming because it continues to ignore large parts of the recent literature and omit what it can’t model.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.
In terms of real world warming and its impact on humans, the ECS is a mostly theoretical and oversimplified construct — like the so-called spherical cow. The ECS tells you how much warming you would get IF we started slashing emissions asap and stabilized carbon dioxide concentrations in the air around 550 parts per million (they are currently at 400 ppm, rising over 2 ppm a year, and accelerating) — AND IF there were no slow feedbacks like the defrosting permafrost.
The climate however is not a spherical cow. Every climate scientist I’ve spoken to has said we will blow past 550 ppm if we continue to put off action. Indeed, we’re on track for well past 800 ppm. And a 2012 study found that the carbon feedback from the thawing permafrost alone will likely add 0.4°F – 1.5°F to total global warming by 2100.
So the alarming disruption in our previously stable, civilization-supporting climate depicted in the top figure is our future. On our current emissions path, the main question the ECS answers is whether 9°F warming happens closer to 2080, 2100, or 2120 — hardly a cause for any celebration. Quite the reverse. Warming beyond 7F is “incompatible with organized global community, is likely to be beyond ‘adaptation’, is devastating to the majority of ecosystems & has a high probability of not being stable (i.e. 4°C [7F] would be an interim temperature on the way to a much higher equilibrium level,” as climate expert Kevin Anderson explains here.
Dr. Michael Mann emailed me:
“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.”
As for the seeming slowdown in global warming, that turns out to be only true if one looks narrowly at surface air temperatures, where only a small fraction of warming ends up. Arctic sea ice melt has accelerated. Disintegration of the great ice sheets of Greenland and Antarctica has sped up. The rate of sea level rise has doubled from last century.
Finally, very recent studies of the ocean, which has absorbed the vast majority of the heat, also show global warming has accelerated in the past 15 years. Sadly, the AR5 appears to have stopped considering new scientific findings before the publication of this research.
Ocean Heat Content from 0 to 300 meters (grey), 700 m (blue), and total depth (violet) from Ocean Reanalysis System 4.
Reuters notes that climate scientists are “finding it harder than expected to predict the impact in specific regions in coming decades.” This regional uncertainty is not surprising but still quite alarming. Indeed, it is a key reason adaptation to climate change is so much more difficult and expensive than simply reducing greenhouse gas emissions.
After all, if you don’t know where the next super-storm or super-heatwave is going to hit, you pretty much have to prepare everywhere. As a major 2011 study by Sandia National Laboratory concluded, “It is the uncertainty associated with climate change that validates the need to act protectively and proactively.” That study found because of “climate uncertainty as it pertains to rainfall alone, the U.S. economy is at risk of losing” a trillion dollars and 7 million American jobs over the next several decades.
On this point, climatologist Kevin Trenberth e-mailed me:
“We can confidently say that the risk of drought and heat waves has gone up and the odds of a hot spot somewhere on the planet have increased but the hotspot moves around and the location is not very predictable. This year perhaps it is East Asia: China, or earlier Siberia? It has been much wetter and cooler in the US (except for SW), whereas last year the hot spot was the US. Earlier this year it was Australia (Tasmania etc) in January (southern summer). We can name spots for all summers going back quite a few years: Australia in 2009, the Russian heat wave in 2010, Texas in 2011, etc.
Similarly with risk of high rains and floods: They are occurring but the location moves.”
The point is, we know that many kinds of off-the-charts extreme weather events will get more intense, longer lasting, and more frequent — in fact, they already are. But we don’t know exactly where and when they will hit, which means adaptation requires pretty much everybody, everywhere to plan the worst-case. Just when you think the Jersey shore is very unlikely to be hit by a superstorm, along comes Sandy.
I very much doubt the IPCC’s Fifth Assessment Report will move the needle on climate action because of its inadequacies; because the media has scaled back climate coverage and let go of its best climate reporters; and because the fossil fuel funded disinformation campaign will try to exploit those first two problems to make it seem like this report gives us less to worry about, when it simply underscores what we have known for a quarter-century. Continued inaction on climate change risks the end of modern civilization as we know it.
Joe Romm is a Senior Fellow at American Progress and is the editor of Climate Progress. He holds a PhD in Physics.