Calculating A Global Carbon Budget

If humanity wants to mitigate climate change, it must calculate a global carbon budget and then allocate that budget among regions or countries. Put aside, for a moment, your (justified) skepticism that governments around the world (especially ours in the US) will ever face up to this fact (because it would inevitably lead to limits that would require, um, sacrifice by the SUV- and meat-worshipping American public, not to mention a complete eradication of all wrong-headed Tea Party beliefs). Because it is a mental exercise that is worth exploring on the off-chance that the effects of climate change start to get bad enough that publics and political leaders wake up.

Calculating how much carbon we can emit before warming the atmosphere beyond the 2 degree Centigrade target that has, rightly or wrongly, become the consensus target is not easy. So many subjective variables. But different scientists and working groups have calculated a range of estimates, and journalist Fred Pearce has an excellent article at Environment 360, explaining those estimates:

The IPCC’s first analysis was included in its fifth scientific assessment of climate change, published in September 2013 and reiterated in the synthesis report released last Sunday. It suggested that a two-thirds chance of keeping warming below two degrees required the world to limit its total carbon emissions since 1860 to no more than a trillion tons of carbon. Of this grand all-time total, 515 billion tons had already been emitted by 2011. So, according to the IPCC, we have just under 500 billion tons of our budget left. Then we have to stop. Totally.

The synthesis report said that fossil-fuel power generation would have to be “phased out almost entirely by 2100″ — unless the largely untried technology of capturing CO2 emissions and burying them out of harm’s way could be deployed on a massive scale. Without a drastic slowdown in emissions within the next decade, the phase-out date could happen much earlier, probably before 2050.

The arithmetic seemed straightforward enough. But carbon budget numbers since quoted by other sources do not all follow this IPCC bottom-line figure. They reveal a bewildering array of different estimates for our remaining budget. Among environmental groups, the World Resources Institute (WRI) sticks with the IPCC estimate that we have 485 billion tons left. But other environment groups quote other numbers. For instance, Greenpeace and WWF say 350 billion tons.

Scientists are even less coordinated. A big study in Nature Climate Changein September by Michael Raupach of the Australian National University in Canberra and others, quotes 381 billion tons. The International Institute for Applied Systems Analysis, a think tank based in Laxenberg, Austria, and the Global Carbon Project says we have 327 billion tons to go. While the International Geosphere-Biosphere Programme, an international research consortium based in Sweden, say 250 billion tons.

To confuse things further, another blue-chip study, published last December by Jim Hansen of the Earth Institute at Columbia University and others, argued that we could emit a further 350 billion tons and still keep below 1.5 degrees of warming.

Simple, right? Okay, not really. But you have to start somewhere. Even more difficult is the question of how yo allocate whatever carbon budget you have left among advanced and developing countries. The fair way to do it would be to include historical emissions, so countries that pumped lots of carbon into the atmosphere while achieving great wealth (like the US), would have to figure out how to sharply curtail emissions while developing countries would have more leeway to emit carbon as they grow their economies further. Or rich, developed countries could buy carbon permits from developing countries who have lots of carbon budget left, which would help those countries reduce poverty and achieve more stable, productive economies. But you can imagine how that idea would play in the US Congress.

I don’t have much faith that the United States and other developed nations will pursue limits that are either sufficient or fair (though I will continue to support and vote for any politician who takes climate change seriously). But I am interested in trying to calculate what an individual carbon budget would look like if we did in fact set global limits that were fair and meaningful. And then exploring what it would take to get my budget down to that level. That would give anyone who wants to stop being part of the problem, who wants to be an Earthist, a target they can aim for. Should be fun, er interesting.

Superstorm Sandy And Global Warming II

Already getting some pushback from wannabe deniers, so I thought I would put this analysis from Scientific American out there as well. The key section:

The hedge expressed by journalists is that many variables go into creating a big storm, so the size of Hurricane Sandy, or any specific storm, cannot be attributed to climate change. That’s true, and it’s based on good science. However, that statement does not mean that we cannot say that climate change is making storms bigger. It is doing just that—a statement also based on good science, and one that the insurance industry is embracing, by the way. (Huh? More on that in a moment.)

Scientists have long taken a similarly cautious stance, but more are starting to drop the caveat and link climate change directly to intense storms and other extreme weather events, such as the warm 2012 winter in the eastern U.S. and the frigid one in Europe at the same time. They are emboldened because researchers have gotten very good in the past decade at determining what affects the variables that create big storms. Hurricane Sandy got large because it wandered north along the U.S. coast, where ocean water is still warm this time of year, pumping energy into the swirling system. But it got even larger when a cold Jet Stream made a sharp dip southward from Canada down into the eastern U.S. The cold air, positioned against warm Atlantic air, added energy to the atmosphere and therefore to Sandy, just as it moved into that region, expanding the storm even further.

Here’s where climate change comes in. The atmospheric pattern that sent the Jet Stream south is colloquially known as a “blocking high”—a big pressure center stuck over the very northern Atlantic Ocean and southern Arctic Ocean. And what led to that? A climate phenomenon called the North Atlantic Oscillation (NAO)—essentially, the state of atmospheric pressure in that region. This state can be positive or negative, and it had changed from positive to negative two weeks before Sandy arrived. The climate kicker? Recent research by Charles Greene at Cornell University and other climate scientists has shown that as more Arctic sea ice melts in the summer—because of global warming—the NAO is more likely  to be negative during the autumn and winter. A negative NAO makes the Jet Stream more likely to move in a big, wavy pattern across the U.S., Canada and the Atlantic, causing the kind of big southward dip that occurred during Sandy.

And I suppose I should also add this analysis by NASA’s James Hansen, who has studied (and worried about) climate change more than any scientist on the (warming) planet. Here’s the guts of what he has to say:

In a new analysis of the past six decades of global temperatures, which will be published Monday, my colleagues and I have revealed a stunning increase in the frequency of extremely hot summers, with deeply troubling ramifications for not only our future but also for our present.

This is not a climate model or a prediction but actual observations of weather events and temperatures that have happened. Our analysis shows that it is no longer enough to say that global warming will increase the likelihood of extreme weather and to repeat the caveat that no individual weather event can be directly linked to climate change. To the contrary, our analysis shows that, for the extreme hot weather of the recent past, there is virtually no explanation other than climate change.

The deadly European heat wave of 2003, the fiery Russian heat wave of 2010 and catastrophic droughts in Texas and Oklahoma last year can each be attributed to climate change. And once the data are gathered in a few weeks’ time, it’s likely that the same will be true for the extremely hot summer the United States is suffering through right now.

The resistance to both the logic and the science of global warming and weather is stupefying to me. But not surprising, sadly. We are a species that is sleepwalking through history.