95% certainty humans causing global warming, per new UN climate report

According to the just-issued United Nations climate change report, the odds that humans are causing global warming has increased to a greater than 95% certainty. Yes, they’ve looked hard at the evidence, and yes, we’re the perp.

In effect, we’re de-terraforming the planet — making it less and less hospitable as a place for our species to live.

I’ve been writing about climate lately for a reason (well, several). One is that we’re on the verge of seeing full new report from the IPCC (the United Nations Intergovernmental Panel on Climate Change).

The report is in four volumes, three covering some aspect of climate change, and one a synthesis of the others. Volume I, from the IPCC Working Group 1, deals with the physical basis — the physical evidence that climate is changing and (conservative) predictions about how much it will continue to change under a number of scenarios.

The full Volume I report is out; the rest are due in 2014. To read just the Summary for Policymakers, click here (pdf). My discussion of IPCC climate scenarios from previous reports is here.

The bottom line from the Volume I Summary: It has been determined that humans are now 95% certain (“extremely likely”) to be causing global warming, up from just “very likely” (>90%) as stated in the previous report (AR4).

The main conclusions from the Summary for Policymakers

I’ll let Real Climate give the primary conclusions from the report. (I’ll have my own analysis at a later time.) My emphasis below:

It is now considered even more certain (> 95%) that human influence has been the dominant cause of the observed warming since the mid-20th century. Natural internal variability and natural external forcings (eg the sun) have contributed virtually nothing to the warming since 1950 — the share of these factors was narrowed down by IPCC to ±0.1 degrees.

“Forcings” is a key term in this literature, so you’ll see it a lot. The meaning is simple — something that forces a change. Greenhouse gases are a “forcing” — they force the air to retain heat. The sun is a forcing; it forces radiant energy into the climate system. The deforestation of the globe is a forcing; it reduces the CO2-absorbing effect of trees. And so on.

What the above says is that the “forcing” effect of natural external factors (non-man-made) is ± 0.1°C. The rest of the roughly 1°C warming is us.

About the scenario predictions:

The future warming by 2100 – with comparable emission scenarios – is about the same as in the previous report. For the highest scenario, the best-estimate warming by 2100 is still 4°C [measured from an already warmer 1980-1999, not 1800] …

They chart that here. Again, note that “zero” on this chart is much higher than the pre-Industrial norm — and that +4°C warming (+another 0.8°C warming for the shift in baseline from 1800 = roughly +5°C warming) measures just the middle of range for the “highest scenario.” As a worst case, that scenario still predicts that a worrisome +7°C is possible. As the report says, not much has changed in that regard.

More on the scenarios later, as I analyze the new report. I’ll leave you to read the rest — there’s more on sea level rise, ice sheet degradation, and so on, in the Real Climate review.

As concerning as the new report is, it’s still a conservative report

Scientists are conservative. They like to say things with certainty, or add the degree of uncertainty to their conclusions. And with climate, they’re always wrong to the slow side — things are happening faster than all predictions.

Sea ice is an excellent example. This is predicted versus actual (observed) loss of Arctic sea ice from the Copenhagen Diagnosis (click to enlarge):

Arctic sea ice — projected vs. observed

Arctic sea ice — projected vs. observed

See what I mean? Conservative. Here’s how Real Climate puts it:

That the IPCC often needs to correct itself “upward” is an illustration of the fact that it tends to produce very cautious and conservative statements, due to its consensus structure – the IPCC statements form a kind of lowest common denominator on which many researchers can agree. The New York Times has given some examples for the IPCC “bending over backward to be scientifically conservative”. Despite or perhaps even because of this conservatism, IPCC reports are extremely valuable – as long as one is aware of it.

and George Monbiot puts it this way (my emphasis):

Already, a thousand blogs and columns insist the Intergovernmental Panel on Climate Change‘s new report is a rabid concoction of scare stories whose purpose is to destroy the global economy. But it is, in reality, highly conservative.

Reaching agreement among hundreds of authors and reviewers ensures that only the statements which are hardest to dispute are allowed to pass. Even when the scientists have agreed, the report must be tempered in another forge, as politicians question anything they find disagreeable: the new report received 1,855 comments from 32 governments, and the arguments raged through the night before launch.

In other words, it’s perhaps the biggest and most rigorous process of peer review conducted in any scientific field, at any point in human history.

All you need to know — there’s an inherent conservative bias in the IPCC process, and it’s still a frightening report. Take out that conservative bias as you read it. Always consider, as I do, the worst-case predictions and you’ll be right more often than not.

Not sure? Look at that sea ice chart again.

Time to get moving, I think. Or better, time to get other people aware that it’s time to get moving. Because if we don’t force our carbon-addicted betters to act, it’s going to be a different world. They’re not going to stop being money-freaks on their own. This will take some pressure. You can help by teaching others that we need to act now. Zero New Carbon, that’s the ticket.

At some point, climate awareness — climate panic — will reach critical mass. You can help. We want that panic, that need, to occur before it’s too late to stop the process.

GP

To follow or send links: @Gaius_Publius


Gaius Publius is a professional writer living on the West Coast of the United States.

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