Paris - When 195 nations clinched the Paris Agreement in December, it was heralded by some as a monumental achievement - the beginning of a process that would roll back the poisonous fruit of humankind's shortsightedness. Others viewed it as too little, too late.
As officials converge this week on the United Nations for the signing ceremony, ominous reports in the four months since the deal have buttressed the doubters: Global warming may hit geological hyperspeed within decades. Nasa is projecting that 2016 will break the annual heat record for the third year running; Greenland's ice sheet is experiencing springtime melt weeks earlier than average; and much of West Antarctica is at risk of slipping into the Southern Ocean by 2100, adding a metre to global sea levels. Coastal cities home to millions of people may be underwater during the lifetimes of those born today.
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The pact “might not be enough, especially in terms of sea-level rise”, said Rob DeConto, a geoscientist at the University of Massachusetts-Amherst. DeConto co-wrote the Nature study in March warning of Antarctica's fate. “We really need to go to zero emissions as soon as possible.”
The earth is almost 1 degree centigrade (1.4 Fahrenheit) warmer than it was before the industrial revolution. The Paris accord, at its heart, is about how much warmer we will allow it to become as we retrofit economies to burn less fossil fuel. The negotiators agreed to hold “the increase in the global average temperature to well below 2 degrees centigrade above pre-industrial levels, and to pursue efforts to limit the temperature increase to 1.5 degrees centigrade”.
Scientific disagreements remain, but whether to act isn't one of them. The most important point of contention is precisely how sensitive the climate is to carbon dioxide. The answer will determine how much time we have left to avoid excessive risk of catastrophe (or, in fact, whether there is any time left at all). Climate Action Tracker is a research group funded by the Children’s Investment Fund Foundation and ClimateWorks. In December, its analysts published estimates of what the national climate pledges in Paris add up to. The answer? Not enough. The world handily overshoots the potentially dangerous “safe” zone of 2 centigrade warming; the lower target of 1.5 centigrade is fantasy.
Luckily, the Paris accord includes a five-year review process, which allows negotiators to tighten their national commitments over time. And there's no way to quantify how the treaty's indirect effects - political capital for activists, changes in consumer energy choices, a renewed push for technological advances - may create opportunities to nudge emissions lower.
The other good news, if you can call it that, is that the gloomy data of 2016 doesn't make things worse. It just affirms what many already suspected: Paris is not enough.
The basics of climate science - more carbon dioxide means more heat, which means less ice, which means higher seas, and so on - don’t change on a weekly or monthly basis. In fact, the span of estimates for how sensitive the climate is to more carbon dioxide hasn't changed much in at least two decades.
“It’s not clear whether a single study, no matter how well-conducted, represents the ‘latest science’,” said Kate Marvel, a scientist at Nasa’s Goddard Institute for Space Studies. Science is a cumulative thing. Marvel addressed the influence that any individual paper might have on the thorny topic of clouds and climate change (There was one this month). “No single study is going to cause us to be all, ‘Stop the press! Revise the Paris Agreement!’”
Rather, the most relevant knowledge is already baked into what policymakers are reading. William Nordhaus, Sterling Professor of Economics at Yale University, developed a leading research tool for climate change, the Dynamic Integrated Model of Climate and the Economy. The latest hot papers may not add much to the big picture, which Nordhaus described in his 2013 book Climate Casino as stunning in its simplicity: “It is that the average temperature of the earth changes with the relative concentration of CO2 in the atmosphere.”
Such clarity, however, doesn't help with the additional problem underlying many proposals to advance the Paris accord. Scenarios generated by climate researchers have to start somewhere, and most begin with a false assumption - that the world has a universal carbon price, or an amount above the market cost of coal, gas, or oil that factors in future damage, according to a commentary this month in Nature Climate Change.
There are regional carbon prices, such as those imposed in the European Union, and sub-national ones, like those of California or British Columbia. Some are market-based and allow emissions-permit trading. Others are just taxes. Imposing a global carbon price like these wasn’t even on the table in Paris.
The Intergovernmental Panel on Climate Change looked at 116 scenarios that might keep the world under the 2 degrees-centigrade threshold, wrote Glen Peters, of the Centre for Climate and Environmental Research in Oslo. Seventy-six of those assume “globally uniform carbon prices in 2010.” Twenty-four simulate a global price beginning in 2020, and 15 anticipate one in 2030.
While the accord signed this week at the UN will carry significant geopolitical weight, Peters warns that future climate projections must reflect the real world. How easy (or difficult) is it to actually build nuclear plants? What if catching and storing carbon dioxide from coal-plant flues never works? How likely are politicians to adopt aggressive policies that work? Peters suggests the IPCC focus on key research gaps. Nations need a way to measure global temperature rise as the Paris accord is implemented. Scientists and engineers need to go all-in on researching technologies that can remove carbon dioxide from the air directly. Simulating how the global economy will react to diminished use of fossil fuel is useful, but it would be helped if “political feasibility and social acceptability” were more clearly written into the models.
“There is an urgent need for scenarios based on more realistic policy assumptions,” Peters wrote.
BLOOMBERG