Limping to Paris
Moving the Climate Goalposts

It seems the closer we get to the much-hyped climate summit in Paris, the fuzzier the numbers seem to become. The UN’s own climate chief has previously written off working towards averting 2 degrees Celsius of warming as compared to pre-industrial levels (a benchmark scientists have rallied around as a kind of threshold past which the effects of climate change get scarier). But a recent UN Environment Program (UNEP) report isn’t ruling that 2C target out as we head into what’s being heralded as a historic conference in Paris later this month. As the AP reports, UNEP is able to do that by backloading emissions cuts in its models:

In its first four annual emissions reports in 2010-2013, the United Nations Environment Program said emissions must not exceed 44 billion tons in 2020 for the world to limit global warming to 2 degrees C (3.6 degrees F). But with real-world emissions rising far beyond that level, UNEP has since last year downplayed its focus on 2020 as a make-or-break year for emissions reductions.

In this year’s Emissions Gap report, a summary of which was released Friday, UNEP says the world can still reach the 2-degree target with emissions of 52 billion tons by 2020, which is just slightly below today’s level. The new analysis assumes that emissions cuts will drop faster after 2030 than was assumed in previous reports.

It looks a lot like UNEP is fiddling with the conditions of its climate modeling in order to produce a politically expedient result. There’s something deeply unsettling about the fact that the UN program can revive a goal that seemed to be all but dead these recent months with some behind-the-scenes tinkering.

And that’s not the only bit of news out this week that will make you question our climate models. As Reuters reports, we know precious little about China’s emissions:

No one currently knows how many tonnes of carbon China emits each year. Its emissions are estimates based on how much raw energy is consumed, and calculations are derived from proxy data consisting mostly of energy consumption as well as industry, agriculture, land use changes and waste.

Many outside observers view the accuracy of those figures with skepticism.

Whether you focus on inputs or conditions, there’s plenty to be concerned about when it comes to the state of climate modeling. We can clearly sketch the problem out at the most basic level: Greenhouse gases raise global surface temperatures, and industrialization is rapidly increasing the atmospheric concentration of those problematic gases. Beyond that, though, climate science quickly breaks down into uncertainty, verging on guesswork.

To call this science “settled” is laughable, not just because our best models have failed to predict a recent plateau in warming, but also because our climate may be the most complex system we study. The sheer number of variables, not to mention the interplay and feedback loops that exist between them, has proven time and again complex enough to confound our expectations.

And it certainly doesn’t help when the country that likely emits more than any other is so bad at transparently providing emissions numbers. And while the UN may have hoped its re-jiggered model would inspire hope at the COP21 talks in Paris, all it has really done is shown how tenuous a grasp we have on all of this.

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