Monday, February 16, 2015

Global Air Pollution Has Offset Arctic Warming By 60%


by Gaius Publius

It looks like my two-part Arctic warming and ice-loss discussion is turning into a triptych. Here's a third part, a capper. In the first piece we saw that one of the most rapidly diminishing glaciers in Greenland has dramatically accelerated its destruction. The front face of the glacier took 100 years, from 1901 to 2001, to retreat eight miles — then retreated nine miles in the next ten years. If you do the math, that's a tenfold increase in the average speed during that first 100 years.

(By the way, there's a nice dramatic video in that piece showing the breaking away — "calving" — of a chunk of ice the size of lower Manhattan; click if that intrigues you.)

In the second piece we saw that, thanks to new satellite data, another Arctic glacier is "galloping" to its end; it has lost one sixth of its thickness in two years, and its flow-to-the-sea rate is, again, accelerating — this time by a factor of 25. If you do the math, that glacier will be gone in less than 10 years.

Atmospheric Pollution and Global Warming

I want to round off with this — accelerating Arctic temperature is likely to accelerate again, thanks to efforts to eliminate a major form of air pollution, the flood of soot and other miniscule particles (called "aerosols" in the literature) emitted by burning fossil fuels, especially coal.

In lay terms, the thing that causes smog in cities and near factories (see the picture above) is a major source of global cooling, an offset to the warming caused by carbon emissions. Pollution isn't a complete offset and the earth is still warming; but it's a strong partial offset. "Coal smog" though, for want of a better term, is also killing people, and even China, among the most coal-dependent countries on the planet, is working to eliminate it. The more we succeed at eliminating these particles from the air, the faster global warming will accelerate. It's a devil's dilemma.

The Arctic is particularly vulnerable to this acceleration, since the globe is warming faster in the Arctic than in most other regions. Not good, since increases in Arctic temperature cause changes in the jet stream (atmospheric air flow), the mid-Atlantic Gulf Stream (which keeps northwestern Europe warm), and adds to the number of very severe storms.

Two notes, and then the article. First, about "aerosols" — everything I wrote above is correct, but you should know that the science of aerosols is complicated. (Skip this part if the science is less interesting to you.) To start, there are natural and man-made aerosols, and they act somewhat differently. Natural aerosols come mainly from sources like volcanoes, contain mainly stuff from deep in the earth, and shoot higher into the sky than emissions from coal plants. All of that makes their effect different in several respects, and longer lasting, than the man-made variety. Man-made aerosols, on the other hand, contain somewhat different material, are injected lower into the atmosphere, and are removed from the air more quickly.

And because all aerosols are complex mixtures — composed of a variety of ingredients — aerosol emissions from most sources contain both warming particles (dark, heat-absorbing stuff) and cooling particles (whiter, light-reflecting stuff). All in all, the study of the effect of aerosol emissions on climate is difficult to model, to say the least. Still, what I wrote above is right. The net effect of man-made aerosols, taken en masse, is a strong cooling offset to the greater global warming from carbon emissions.

Second, I don't write about this for doomy reasons. I'm a believer in facing problems, starting with appropriate understanding. We can fix this, but only if we're realistic. Check the bottom of this piece for more.

Without Air Pollution, Global Warming Would Be Twice As Great In the Arctic

Now for the article (my emphasis):
Temperatures in the Arctic are increasing more than twice as fast as the global average. This is known as  Arctic amplification. A primary cause is  diminishing Arctic sea ice: as the ice melts, energy from the sun that would have been reflected away is instead absorbed by the ocean.

A new study, just published in  Nature Climate Change, works out the specific contributions from different influences on temperatures in the Arctic, including natural factors. ...

The research compares three influences on global temperature: human-caused greenhouse gas emissions, human-caused aerosol emissions, and natural climatic variations.

The study looks at surface temperature changes in the Arctic from 1913 to 2012. Comparing historical temperature observations with climate model simulations, the researchers work out the 'fingerprint' of each influence on past temperature changes.

The results show greenhouse gas warming alone would amount to around three degrees Celsius in the Arctic over the last 100 years. But actual observed warming is around 1.2 degrees Celsius. So why the shortfall?

It turns out that the difference is caused by the aerosols emitted alongside greenhouse gases. Aerosols offset about 60 per cent of the warming, causing temperatures to be 1.8 degrees lower than they would otherwise be.
By comparison, natural climatic changes have no discernable impact on long-term warming, the paper finds.
The writer interviewed the paper's lead author and learned this:
[T]he results suggest the cooling effect from aerosols is much larger in the Arctic than elsewhere in the world, [Dr. Mohammad Reza] Najafi adds. A separate study finds aerosols were responsible for offsetting around five per cent of global greenhouse gas warming between 1901 and 2010, and around 27 per cent for the shorter period of 1951 to 2010.
In other words, the more we reduce air pollution from coal plants and other "dirty" sources, the more we increase global warming just from that cause alone. According to Dr. Michael Mann in an interview I recently did with him, global warming is now at roughly +1°C from pre-Industrial times. The IPCC says if we get to +2°C, it will be a disaster (I think that's too conservative, too generous a limit). Eliminating particulate air pollution will warm the planet another 0.27°C at least, to more than +1.27°C, all by itself. And again, the effect on the Arctic would be more than double the overall effect.

If you want to pursue the this further, read the whole article or check out the paper itself. Nature Climate Change is a major publication in the field.

It's Only Over If We Waste Our Chances

This isn't a call to despair. It's a call to action, and a call to be prepared to act effectively. There will be a moment when even Republicans clamor for government to step in and fix things — for example, if Miami were struck by a Haiyan-style hurricane and property values sank to zero, never to return.

At some point the steady stream of people who "get it" will be a flood. There will be a flash-point, something, I guarantee. In that context, I want to repeat what I wrote earlier about collapsing Arctic ice
If people are "getting it" — and believe me, they are — and if collapse of visible and important aspects of our climate system is happening fast and now, this is not just a time of fear. It's a time of unique and valuable opportunity.

Teach into it by talking to everyone you know. Tell them: (1) It's not over yet; just getting there. (2) The only solution is to hit the carbon brakes, hard and now. Not slowly enough to keep Charles Koch in ego- and sociopathic bragging-money — now. (3) If doing that takes a kind of anti–"free market" revolution, what's the downside?

... The downside [of not hitting the brakes fast enough] is a future ice-free planet, and planetary social chaos for those alive today while we get there. Say that when someone asks, "Yeah, but at what cost?" 
Click here for some thoughts on how we get there. It's not an impossible task, and a window will open in which we get one shot at a forceful, united, "gearing up for World War II"–type solution. But I think we get just one shot, and we need to be clear-eyed to make it count. We have to offer the right solution — zero carbon now — not some confused, billionaire-coddling scheme that's doomed to fail.

We will get that shot, I'm convinced of it. Do stay hopeful. But stay unconfused as well.


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