h6. A guest post from Brian Bahnisch on global warming and climate change
On the weekend I decided to revisit the topic of anthropogenically caused global warming and consequent climate change after renewed debate on this site (Parish backs Kyoto) and elsewhere. What follows is some of what I found.
Sir David King, Chief Scientific Adviser to the UK Government, recently advised Tony Blair that climate change was a greater problem for the world than terrorism. While he identifies the range of prospective warming as 1.4 to 5.8C he doesn’t enter into much discussion about its validity. This is a man who doesn’t let the grass grow under his feet, mainly because he can feel the water creeping up his legs already. He points out in an address to the American Association for the Advancement of Science that now something like “10 percent of the housing within England is in flood plains as distinct from 20 years ago”.
In fact the Thames barrier, completed in 1982, at first came into play once in every 3 or 4 years. Now it is used 6 or 7 times a year, each time preventing a flood that would cost $56.7 billion in damage.
His idea is to get ahead of the game, to reduce CO2 emissions unilaterally by 60% by 2050. This will maximize their influence on other countries and make them a mozza through their lead in the appropriate technologies.
He points out that last summer 30,000 people died prematurely in Europe in the heat waves. Mark Lynas in this article reckons that “last year’s heatwave across Europe was so far off the normal statistical scale that climatologists logged it as a once-in-10,000-years event.” That makes it a once per interglacial affair. I’m sure Sir David has worked out that 30,000 is many more than died through international terrorism if you take out state terrorism perpetrated by countries like the US, the UK, Australia and Israel.
Mark Lynas believes that methane burps are a possibility. Since there is calculated to be 10,000 gigatonnes of methane locked up under the oceans and the stuff is 21 times more potent greenhouse-wise than CO2 it is a worry. I’ll just spell that out. Each year we add 6 billion tonnes of carbon to the atmosphere. There is the equivalent of 210,000 billion tonnes of the stuff locked up under the oceans. Is that a worry? Well 251 million years ago according to the work of Michael Benton (see his “When Life Nearly Died: The Greatest Mass Extinction of All Time”, references here, here and here) methane emissions caused about 90% of life on earth to die.
It seems that the temperature may have been 5C or so hotter then. Benton puts the likely cause as a huge volcanic eruption in Siberia. It’s not clear how much the temperature had to do with it, or what might cause smaller burps.
Methane burps may not be a likely scenario, but it seems there is a bias in the way the statistics are collected and presented which favours gradualism and suppresses critical or threshold events associated with ‘abrupt’ climate change.
Of interest is the report of the US National Research Council’s Committee on Abrupt Climate Change (2002). On page 7 of the Executive Summary they say: “Current practices in the development and use of statistics related to climate and climate-related variables generally assume a simple, unchanging distribution of outcomes.” Not being a scientist I don’t understand what that means. I do, however, understand the next sentence: “This assumption leads to serious underestimation of the likelihood of extreme events” a situation that obviously needs rectifying.
A man who understands that there may be critical phases in the process and points of no return is James Hansen. His article ‘Can we defuse the Global Warming time Bomb?’ appeared in the March issue of the Scientific American. A larger version in pdf format is available here.
Hansen reckons the main culprit is coal and the effect to worry about is rising sea levels, especially through ice sheet degradation. He points out that forming ice sheets, glaciers etc is a dry process and takes centuries, if not millennia. Degradation and melting is a wet process and much more rapid. Not enough is known about the process of degradation and when a critical point of no return may be reached.
For me his other important message is that climate forcing operates over a very long time-scale (a century or so to reach a new equilibrium if we stop emission increases now?). Hence we have 0.4 to 0.7C warming already in the pipeline if we stop increases now. We are currently forcing at the rate of about 1 watt per square metre of the earth’s surface, with an additional 2 watts per square metre likely in the next 50 years. As watts per m2 convert to about 0.75C of warming, this gets you, if you add all three, to 2.8C in 50 years. I’m not sure whether you do add all three, the first two components may be coincidental. If so you get 2.05C.
Hansen thinks we should contain additional forcings to 1 watt per square metre, or half what he thinks will happen. Any more could put us in a critical meltdown phase, when the process may be unstoppable with significant consequences for the earth’s capacity to sustain life as now.
It’s worth noting that Hansen considers the IPCC projections unduly pessimistic wrt emissions and temperature change. Possibly we’ll lob in the lower range of their forecasts. He is very clear, however, that the IPCC has underestimated sea level rising. Apparently they discounted melting and concentrated on thermal expansion.
I am impressed with Hansen, especially his care about what we know, what we are uncertain about, what we don’t know and the interactivity between various factors. In particular he appreciates that there may be smoothing in the models that obscures the unlinearity of reality.
So that’s some of what I found rummaging around this weekend. I’m not a scientist but I wouldn’t be surprised if there was a paradigm shift or two around the corner. I do not think we can wait for science to provide final answers, however, lest we find ourselves (well, some of humanity) 5 meters under water or with a mile-high slab of ice over Manhattan (Hansen says it can’t happen, but he too, may be surprised).
There is a debate about what constitutes dangerous anthropogenic interference (DAI) which turns out to be a matter of ethics as much as science. I invite you to have a look at a brief introduction to the subject here. The levels nominated by various authorities are surprisingly low.
Given the science already to hand I find the suggestion that we take no special action difficult, indeed impossible to justify ethically.