Antarctica linked to Arctic

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Waters in the Arctic Ocean continue to warm up. Very warm waters from the North Atlantic and Pacific Ocean are invading the Arctic Ocean.

Waters in the North Atlantic and in the North Pacific are very warm, due to a number of reasons.

What is happening in the oceans is very important in this respect. As discussed in earlier posts, most of the extra heat caused by people's emissions goes into the oceans.

The great ocean conveyor belt (Thermohaline Circulation), brings warm water from the southern hemisphere to the northern hemisphere.

The Gulf Stream is the North Atlantic leg of the great ocean conveyor belt, and it brings dense, salty water from the North Atlantic into the Arctic Ocean.

Saltier water is denser than fresher water because the dissolved salts fill interstices between water molecules, resulting in more mass per unit volume.

Very dense ocean water can be found in the North Atlantic because the North Atlantic has high salinity, due to high evaporation rates, while salty water is also coming from the Mediterranean Sea.

As also discussed in an earlier post, this dense, saltier water sinks in the North Atlantic, accumulating in deeper water.

By contrast, much of the Arctic Ocean has low salinity, due to ice melt and river runoff.  As it enters the Arctic Ocean, the warm and dense water from the Atlantic thus dives under the under the sea ice and under the less salty surface water in the Arctic Ocean.

In conclusion, much of the heat resulting from people's emissions accumulates in the North Atlantic and also ends up in the Arctic. This partly explains why surface temperatures are rising much faster at the poles, as illustrated by the NOAA image below.

There are further reasons why surface air temperatures elsewhere (other than at the poles) are rising less rapidly than they did, say, a decade ago. As also discussed by Andrew Glikson in the post No Planet B, the increased amounts of sulphur emitted by the growing number of coal-fired power plants and by the burning of bunker fuel on sea is (temporarily) masking the full wrath of global warming.

Another reason is the growth of the sea ice around Antarctica, as illustrated by the CryosphereToday image on the left.

Melting takes place both in the Arctic and on Antarctica, but more so in the Arctic. Recent research of CryoSat-2 data reveals that Greenland alone is now losing about 375 cubic kilometers of ice annually, while in Antarctica the annual volume loss now is about 125 cubic kilometers.

Currents also distribute ocean heat in ways that make the Arctic warm up more than twice as rapidly as the Antarctic. In a recent paper, John Marshall et al. further suggest that ozone depletion also contributes to this.

All this makes that, while the jet streams on the northern hemisphere are circumnavigating the globe at a slower pace, jet streams on the southern hemisphere are getting stronger, making it more difficult for warm air to enter the atmosphere over Antarctica, while the stronger winds also speed up sea currents on the southern hemisphere. This makes the sea ice around Antarctica grow, and as the sea ice spreads further away from Antarctica, temperatures of surface waters around Antarctica are falling.

Growth of the sea ice around Antarctica makes that more sunlight is reflected back into space. There now is some 1.5 million square kilometers more sea ice around Antarctica than there used to be. The albedo change associated with sea ice growth on the southern hemisphere can be estimated at 1.7 W/sq m, i.e. more than the total RF of all CO2 emission caused by people from 1750 to 2011 (IPCC AR5).

The rapid growth of sea ice on the southern hemisphere alone goes a long way to explain why, over the past three months, surface air temperatures have not been much higher than they used to be, both globally and in the Arctic, as illustrated by above NOAA image. What has also contributed to warmer temperatures around latitude 60 on the northern hemisphere is the fact that methane has accumulated in the atmosphere at that latitude, as discussed in earlier posts.

Arctic SST far exceed anything ever seen in human history

So, does the sea ice on the southern hemisphere constitute a negative feedback that could hold back global warming? It doesn't.

It may temporarily keep surface temperatures close to what they used to be, as the sea ice reflects lots of sunlight back into space, but at the same time ocean temperatures are rising strongly, as the sea ice also prevents heat from radiating out of the waters around Antarctica.

The latter also helps explaining the colder surface temperatures over those waters.

Much of this additional ocean heat has meanwhile been transported by the great ocean conveyor belt to the northern hemisphere.

No time before in human history has such a huge amount of ocean heat accumulated in the North Atlantic and the North Pacific. This heat is now threatening to invade the Arctic Ocean and trigger huge temperature rises due to methane eruptions from the seafloor.

The situation is dire and calls for comprehensive and effective action, as dicussed at the Climate Plan blog.

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Dealing with Climate Change: Getting There from Here

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Engineers are people of action, not just words.  But even if we believe what we are often told about climate change, it's not at all clear what we should do about it.

Last week, I attended a meeting at which a highly credentialed professional meteorologist outlined the history of the science of climate change from the nineteenth century to the present.  Prof. Andrew Dessler of Texas A&M's Department of Atmospheric Sciences described how as long ago as the 1890s, Swedish scientist Svante Arrhenius calculated that the small concentration of carbon dioxide in the atmosphere (then around 300 parts per million) had a disproportionate effect on the earth's temperature.  Regular monitoring of this concentration began in the 1950s, and by then it was clearly understood that more carbon dioxide means higher temperatures.  Dr. Dessler said that for at least fifty years, there has been a consensus that the present human-caused increase in carbon dioxide in the air will eventually lead to a rise in global average temperatures of "a few degrees C." 

So far I was with him.  Other things being equal (which they never are), more greenhouse gases in the air (of which carbon dioxide is one) means the planet gets warmer.  But then he started talking about cigarette smoking, and how the tobacco industry mounted a cynical disinformation campaign in the 1960s against the overwhelming evidence that smoking caused lung cancer and heart disease.  Because it took about forty years for the scientific truth to change public policies (you began to see smoke-free campuses and workplaces only about ten years ago), Dr. Dessler thinks it may take that long for the U. S. to get serious about global warming.  Personally, I think it will take longer than that, because the two cases are more different than they are similar.

As someone else in the audience pointed out, smoking has highly specific individual consequences.  As long ago as 1964, anyone who read a newspaper knew that by smoking, you made it a lot more likely that you would die early and fast, the way my father died of lung cancer at 57 only a year after he was diagnosed.  If driving a Humvee increased your personal chances of having your own house wrecked by a tornado by the same degree as smoking increases your chances of causing lung cancer, what would happen?  Well, for one thing, Humvee owners would have a lot of trouble getting home insurance.  And sales of Humvees would fall.

But in contrast to the smoking-cancer tie-in, the actions that contribute to climate change, and the possible (I emphasize "possible") consequences, are about as far removed as you can get and still stay on the same planet.  From what little I know about the matter, it appears that the most widespread and likely consequence of letting the earth's average temperature rise a few degrees Celsius is that a lot of ice will melt, water will expand, and the ocean's average levels will rise.  Let's leave aside all the other stuff—species extinction, storms, and other changes in weather patterns—and concentrate on just that one thing.

About 44% of the world's population in 2010 lived within 150 km (94 miles) of the sea.  And many of the world's most populous cities are coastal ones, or so close to the coast that a significant rise in ocean level would cause them major problems.  Now if all the ice in Antarctica melted, the ocean's level would rise some 61 meters (200 feet).  So in that case, good-bye Hong Kong, New York, and Florida.  But to my knowledge, no serious scientist has proposed that the entire ice sheet covering Antarctica is going to melt because of human-induced climate change.  So the fact is that you have a range of estimates of how much the oceans will rise, but all of them are much less than 61 meters.  They may be well-educated estimates, but that's all they are—estimates.

So instead of a single increased chance that you, individually, will suffer about the most serious consequence you can encounter—death—as a result of your individual actions, your individual motivation to do something about climate change is that somebody, somewhere, possibly but not certainly near a coastline, might eventually have to move or suffer an increased chance of getting flooded out in a storm.  And that person might be you, but not for another few decades, anyway.  And even if you become a hyper-climate-conscious zero-carbon-footprint fanatic, your solitary actions will be fruitless unless billions of people all across the world do likewise, or at least move in that direction.

Personal versus impersonal, individual versus transnational, death versus some fuzzy probabilistic consequence for many people you will never meet—at the point of political action, the analogy between smoking and burning fossil fuels collapses.  There is also the little matter of the difference in economic importance of the two industries in question.  If the entire tobacco industry vanished tomorrow, life could go on more or less normally for most of us, but if the entire fossil-fuel industry vanished tomorrow, a large number of us would die in a matter of weeks for lack of basic necessities.  That is a big downside cost to the proposal to something about climate change fast.

Prof. Dessler sees a global carbon tax as the way forward.  He thinks if the U. S. slapped a big carbon tax on imports, that the rest of the world would fall in line and come along quietly.  A global tax high enough to put significant brakes on fossil fuel consumption now would likely do something similar to what the Smoot-Hawley Tariff of 1930 did.  Most economists believe that those extremely high U. S. tariffs contributed significantly to the worldwide depression of the 1930s, and punitive carbon taxes imposed on countries that don't get in line with reduction in fossil-fuel use would probably trigger a global depression that would make the 1930s one look like a mild headache in comparison.

From an engineering point of view, achieving the goal of transitioning from a global economy based on fossil fuels to one in which fossil-fuel use is cut to a small fraction of its present rate is logically possible.  But achieving it in a way that is just and fair, and imposes hardships less than those otherwise suffered from whatever climate change would result, is an immensely challenging technical and political task, and would require a degree of coordination and cooperation that is unprecedented in world history. 

Maybe it will happen.  But if history is any guide, something really awful, and unequivocally attributable to climate change, will first have to happen worldwide, in order to create the political will to act.

Sources:  Prof. Andrew Dessler spoke at the Lone Star Historians of Science meeting at Texas A&M University on Apr. 11, 2014.  I referred to Charles Krauthammer's column on climate change carried by the Washington Post on Feb. 20, 2014 at http://www.washingtonpost.com/opinions/charles-krauthammer-the-myth-of-settled-science/2014/02/20/c1f8d994-9a75-11e3-b931-0204122c514b_story.html, and Daniel Yergin's history of climate change at http://danielyergin.com/history-of-climate-change/. 

The statistic about ocean levels and Antarctica is from http://science.howstuffworks.com/environmental/earth/geophysics/question473.htm.  And for how a qualified opponent of the conventional view of climate change, Prof. William Happer, was received at another professional meeting, see my blog "When Scientists Aren't Scientists" on Oct. 7, 2013.

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