Saturday, February 19, 2011

An inconvenient future

A review of the geological record (i.e. our climate crystal ball) points to a torrid Earth

As we all know, climate change is already here and affecting our lives. Extreme weather, hotter average temperatures, desertification, coral bleaching, wildfires ... on and on it goes. The biosphere is in crisis, and we will bear substantial costs, though probably not the extinction that is the fate of so many of our fellow organisms. A recent story told of a polar bear who took off from shore with her cub towards the pack ice, only to find it over 400 miles away, herself emaciated and her cub dead.

A recent brief review in science (news stories here, here) laid out the trajectory where we headed, using Earth's climate 35 million years ago as its benchmark. CO2 was at roughly 1000 ppm at that time, compared to the roughly 400 ppm we are at now. The recent preindustrial level was roughly 280 ppm, and assuming we are near peak oil, and nowhere near peak coal, business as usual gets us to 1000 ppm CO2 by 2100 (which equals 0.1% of the atmosphere).

CO2 trajectories under various scenarios of public action.
One can not overemphasize how big these changes will be. The paper discusses them in terms of °C, (as most scientists do), which for US readers has a seriously diminishing effect, reducing the absolute values as well as using unfamiliar units. So I will convert all values to Fahrenheit (which incidentally is just as foreign an invention as the Celsius scale, only by a German rather than a Swede!). The paper assumes that CO2 is the main variable forcing climate change, which is consistent with everything we know to date about these geologic eras. It also synthesizes various geological markers of the temperatures and CO2 concentrations which the author and others have spent their careers studying.

Ancient climate data. Top- inferred CO2 concentrations, averaged in green. Bottom, glaciations & ice caps, which are absent at >~800 ppm CO2.
On average, earth was 29° hotter then than it is now. The tropics were 14° hotter (averaging 99.5°), while the poles were 32° warmer, averaging 73°. One can imagine that any kind of polar ice cap is not possible under these conditions. Miami Florida currently has an average annual temperature of 76°. The hottest average annual temperature ever recorded was 94° in Dallol, Ethiopia, in the 1960's.

Getting to these levels will probably take some extra time beyond 2100, due to lags in the climate system, principally the time it will take to melt the South Pole. But one can see that this is a world we do not want to live in. Everyone would want to move to the poles, where there is, frankly, not a lot of room. After the South Pole melts, sea levels will be roughly 230 feet higher than they are now.

Antarctica, melted.
While climate changes like this took millions of years in past epochs, we are imposing this change in a matter of two hundred years, far faster than our fellow earth inhabitants can evolve to keep up. After already causing one extinction event by our prehistoric hunting of large animals over several continents, followed by our destruction of many wild populations in historical time, we will shortly cause another of even more breathtaking scale by our CO2 emissions.

CO2 levels over more recent times, the last 400,000 years.
Once CO2 is at these levels, natural processes will take tens of thousands of years to return it to normal. So we had best come up with atmosphere purifying methods quickly, whether or not we manage to achieve policy changes that reduce our emissions.

These are conservative estimates, since the sun was 0.4% dimmer back in the Eocene era that we are talking about. But, being drawn from our actual climate past, they are very plausable predictions, not dependent on complex modelling and other types of forecasting (which tend to be conservative, actually). Earth has been there before, and while life surely flourished in the Eocene, it was not in the same places as it is now, and was not even the same life that exists now. We are heading into a far, far different world.

It is easy to blanch at this prospect and adopt a deer-in-the-headlights state, each individual being such a small part of this vast and cataclysmic problem/solution. That is why it is particularly important to raise climate change to the top of the political/economic agenda, more so than it is to perform individual mitigation, however laudable. Our collective economic and political structures need to take this seriously before any of our actions can be truly effective.

"Reverently let us invoke the God of our fathers to guide and protect us in our efforts to perpetuate the principles which by his blessing they were able to vindicate, establish and transmit to their posterity. With the continuance of his favor ever gratefully acknowledged, we may hopefully look forward to success, to peace and to prosperity."
  • Bill Mitchell quote of the week:  A graph, which speaks for itself.

  • Plus a bonus quote from FDR:
"We know now that Government by organized money is just as dangerous as Government by organized mob."

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