Cryosphere Math: The Rule of Twos
For the cryosphere, the 2011 UNEP/WMO Integrated Assessment on Black Carbon and Trophosperic Ozone was a vitally important study. Given the brief time I have here today – and perhaps because I have an 11-year-old who is suffering through fractions and multiplication right now — I am going to put this importance in terms of what I’d call cryosphere math: mostly rules of doubles, and halves.
The very general rule of thumb in the cryosphere, whether it is the Arctic or the Himalayas, is that temperature rises are occurring at double the rates elsewhere. More dangerously for future generations like my daughter – who will be exactly my age today in 2050 – the now-agreed goal of a two-degree target does not mean two degrees in the Arctic and Himalayas, but more like four or even five.
This is dangerously high.
Two facts to illustrate this “Rule of Twos,” of changes that have accompanied this rapid rise in temperature already. First, land glacier mass decline in regions throughout the world. There of course exists a fair amount of variability. Nevertheless, scientists see a broad downward trend globally – and in some places like North and South America, huge rates of loss of mass, or the total amount of ice, as well as receding length.
The second indicator: the very rapid decline in Arctic sea ice. 2007 was the previous record, which may well be broken in 2012. Yet what the very low rates in 2007 also did was move the mean: all years since then have been closer to the 2007 minimum than to the previous norm (which was still downwards). Current forecasts are that we will see the first ice-free Arctic summer up there by 2030.
Moving back to the math: double the rates means in essence half the time to deal with the problem. The whole time scale of climate change in the cryosphere is different, and so must our responses be.
That brings us to the good news part of the UNEP Assessment, because what it tells us is that especially in these regions, the short-lived forcers black carbon, ozone and methane are half the problem – and therefore half the solution. We can do something about this!
There is however also good news in the cryosphere rule of twos, and it was illustrated by the 2011 UNEP/WMO Integrated Assement of Black Carbon and Ozone. The Assessment measures led to declining temperatures throughout the globe – but in the Arctic, it was bearly twice that of the global mean, 0.7 degrees versus 0.4 degrees. This difference should hold for other cryosphere regions as well (and ICCI hopes to support work soon to examine this). But if the bad news is that the cryosphere is warming faster than the rest of the world, the good news is that its response to decreases in black carbon and methane is also faster.
This is a huge result – the IPCC in its fourth Assessment (2007) forecast an additional rise of temperature in the Arctic of 1.2 degrees by 2050. That rise will occur even with the aggressive CO2 measures, measures for which I need to make clear ICCI is also working, in the UNFCCC context. But the chemistry of CO2 is such that even a peak in 2020 just won’t decrease temperatures by any significant amount by that half-century mark. The actions named in the Assessment on the other hand would decrease that projected warming in 2050 by almost two-thirds, 7/10 of a degree.
To deal with the parts of climate change affecting the globe between now and 2050, you really need to deal with the whole of the problem, not just halves: aggressive reductions in CO2 and short-lived forcers both. This is why ICCI is involved in everything from support for the prototype methane fund mentioned in the UNEP Action Plan, to campaigns on decreasing use of old woodstoves and agricultural burning in Arctic nations, to the Global Alliance for Clean Cookstoves. All these policy efforts are needful, if we are to preserve the cryosphere.
Finally, I believe the Arctic nations have a special role in this effort. They were the first to recognize the potential of short-lived forcers, with special leadership from Sweden, Norway and the United States. Yet it is truly a global issue, and together with UNEP I hope that Arctic nations will continue to lead, as well as to support actions elsewhere. This is not just for the benefit of the Arctic, but to demonstrate for the rest of the world what can be done to slow temperature rise: and on the cryosphere’s “rule of two’s” time scale.