2 degrees celsius climate target: right or wrong?



Could the 2C climate target be completely wrong?

The global warming goal that nearly 200 governments have agreed on should be ditched, say scientists writing in Nature

Adam Vaughan
theguardian.com, Wednesday 1 October 2014 13.03 EDT

A discarded signboard from People’s Climate March in a trash bin in Manhattan, New York. Photograph: Carlo Allegri/Reuters

In a nondescript conference centre five years ago, as temperatures fell to freezing outside in the streets of Copenhagen and protesters gathered, world leaders did something remarkable: they put a limit on how high temperatures should be allowed to rise as man-made global warming takes hold. It was the first time the nearly 200 countries in the UN climate talks process had put a number on what constituted the limit for dangerous climate change (Germany had done it years before, followed by the EU). And with hindsight, is one of the signal agreements of a summit that was widely derided as a failure. Since then, the 2C target – or obligation, as some in climate diplomacy circles refer to it – has been repeated like a mantra, mentioned thousands of times in newspaper articles and most recently uttered aloud repeatedly last week by heads of state in New York for a climate summit organised by Ban Ki-moon. But two academics in the prestigious journal Nature now argue that the 2C target has outlived its usefulness. They say it should be abandoned and replaced with a series of measures – “vital signs” of the planet’s health. Under the headline, “Ditch the 2C warming goal”, they argue the 2C limit is “politically and scientifically … wrong-headed”, it is “effectively unachievable” and it has let politicians off the hook, allowing them to “pretend that they are organising for action when, in fact, most have done little.” David G Victor, the University of California professor who co-wrote the comment along with former Nasa associate administrator Charles F Kennel, said he felt compelled to speak out after watching climate diplomacy efforts and working on the latest blockbuster report by the UN’s Intergovernmental Panel on Climate Change. “All diplomacy was focused around this goal and yet it struck me as obvious that the emissions trajectories, even if governments made a big effort at controlling emissions, were way off track for 2C.” Working on the IPCC report, he told the Guardian, made him realise the ‘climate establishment’ was “entirely geared to supporting 2C even though nobody had a serious plan for meeting it“. For some in international climate politics, Victor and Kennel’s message of reality, as they call it, is tantamount to heresy. And it has provoked a strong reaction. “The University of California should realise 2C is a fact, not a target,” said Lord Deben, former UK environment secretary and now chair of the UK’s statutory advisers on climate change. “Go above it [2C] and you say something about the world that is intolerable. 2C is dangerous but at least we have some understanding of what that means. To abandon that would seem a most peculiar thing to do.” The 2C mark is often described as the level beyond which disastrous impacts including flooding and heat-waves – and potentially runaway warming as natural ‘feedbacks’ kick in – would take place. …



2°C Or Not 2°C: Why We Must Not Ditch Scientific Reality In Climate Policy

by Joe Romm Posted on October 1, 2014 at 5:01 pm

Global-mean surface temperature 1880-2013. Grey line shows annual values, and the smoothed blue line highlights the long-term evolution. (Via RealClimate using NASA data)

A new Comment piece in Nature argues we should “Ditch the 2 °C warming goal” as a basis for climate change policy. Here’s why the authors, political scientist David Victor and retired astrophysicist Charles Kennel, are wrong — and why “their prescription is a dangerous one,” as a top climatologist told me.
Their core argument, as Nature sums it up, is “Average global temperature is not a good indicator of planetary health. Track a range of vital signs instead.” I’ll discuss below why our global temperature is a perfectly reasonable indicator of planetary health — or rather, of planetary sickness, since we have a fever. First, let’s dispense with the notion that tracking a “range of vital signs” would somehow make it easier for humanity to avoid catastrophe.

Consider that way back in 2009, “a group of 28 internationally renowned scientists identified and quantified a set of nine planetary boundaries within which humanity can continue to develop and thrive for generations to come. Crossing these boundaries could generate abrupt or irreversible environmental changes.”

Unfortunately, we’ve already crossed some key ones, including climate change and rate of biodiversity loss:… Oops. The thing is, five years ago, Nature actually published a major article (and responses) on these “planetary boundaries.” The key takeaways. First, the planet has already overshot multiple boundaries, including climate change (and is close to doing so in a couple more including CO2-driven ocean acidification).

Second, adding more vital signs just gives people more things to argue about, so it is hardly a recipe for faster or more streamlined international action. Indeed, the whole Victor and Kennel approach would be an excuse for more dawdling. They don’t just want to ditch the 2°C limit but they want to replace the entire effort aimed at developing a global plan to avoid that limit culminating in the December 2015 Paris climate conference. Instead, they write, “New indicators will not be ready for the Paris meeting, but a path for designing them should be agreed there.”

Yes, instead of trying to get the world’s leading governments to agree on the commitments needed to avoid crossing the 2°C target, let’s just ask them to agree on a “path for designing” some new targets. So long Miami, New Orleans, and other coastal cities — it’s been good to know you!

As Michael Mann, director of the Earth System Science Center at Pennsylvania State, wrote me:

Giving up on the 2C warming limit, after so much work has been done to motivate this objective and meaningful target for defining dangerous climate change amounts to kicking the can down the road. It simply provides a crutch for those looking for yet another excuse for not doing the tough but necessary work to stabilize greenhouse gas concentrations below dangerous levels. Sure, it’s possible that we will fail to stabilize temperatures below 2C warming even given concerted efforts to lower our carbon emissions, but simply discarding this goal would make failure almost certain.

I’m sure the authors mean well, but their prescription is a dangerous one in my view. TWIMC: The scientific reality is that we are already in overshoot!

So what exactly is wrong with the 2°C target that it should be ditched? Sadly, Victor and Kennel offer a bunch of beyond-dubious arguments: The scientific basis for the 2°C goal is tenuous. The planet’s average temperature has barely risen in the past 16 years These statements are not merely dubious, they are “disingenuous,” to use the word of Stefan Rahmstorf, Co-Chair of Earth System Analysis at the Potsdam Institute for Climate Impact Research, in his debunking post on RealClimate.

It is truly unfortunate that Victor and Kennel perpetuate the myth that there has been some sort of a pause in warming. Nearly a year ago, a journal article explained that a key reason there appears to be a pause is that one of the major temperature data sets ignores all warming in the Arctic (see here). Also, as Rahmstorf notes, it is very widely known that “picking 1998 as start year in this argument is rather disingenuous –- it is the one year that sticks out most above the long-term trend of all years since 1880, due to the strongest El Niño event ever recorded.”

What’s even more bewildering is even to the extent there has been a slowdown in surface air temperature warming during this cherry-picked period that has no bearing on the argument Victor and Kennel are making, as Rahmstorf shows:

They fail to explain why short-term global temperature variability would have any bearing on the 2 °C limit — and indeed this is not logical. The short-term variations in global temperature, despite causing large variations in short-term rates of warming, are very small — their standard deviation is less than 0.1 °C for the annual values and much less for decadal averages (see graph — this can just as well be seen in the graph of Victor & Kennel). If this means that due to internal variability we’re not sure whether we’ve reached 2 °C warming or just 1.9 °C or 2.1 °C — so what? This is a very minor uncertainty.

The argument by Victor and Kennel that there’s no “scientific basis” for the 2°C limit or that it was “uncritically adopted” by governments is thoroughly debunked at length by Rahmstorf (see also Mann’s “Defining Dangerous Anthropogenic Interference).”…

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