How to Think About Climate Risk in the Anthropocene

Increasingly few people believe humans are likely to prevent global temperatures from rising two degrees Celsius above pre-industrial levels. How then should we think about likely impacts — and possible responses? Those were the questions debated at the 2015 Breakthrough Dialogue concurrent session on climate risk.

The panel included: an IPCC-cited climate scientist (and Breakthrough Senior Fellow) Tom Wigley; climate scientist and former US climate advisor David Lea, from University of California, Santa Barbara; environmental economist Richard Tol, whom the IPCC recently selected as a coordinating lead author of their Fifth Assessment Report; and climate policy expert Oliver Geden from the German Institute for International and Security Affairs.

Wigley opened the panel by explaining what “dangerous anthropogenic interference” could mean. He explained a 450 ppm concentration target could stabilize temperatures to two degrees but could still lead to dramatically rising sea levels. Stabilization of both temperature and sea level could require the lowering of atmospheric concentrations of carbon to below 250 parts per million (ppm), which is lower than pre-Industrial levels.

Given the unlikeliness of this occurring, Wigley argued there will need to be adaptation to extreme weather and rises in sea level. Global level action to avoid warming over two degrees “raises the spectre of geoengineering or carbon removal.”

Tol noted that most economic models show that crossing the two-degree limit would only modestly affect aggregated global welfare. A rise in 2.5 degrees over a hundred years, he explained, “will make people [at the end of the century] feel as if they had lost one year of economic growth.”

Climate change is “not the biggest problem for humankind,” in comparison to poverty and indoor and outdoor air pollution. “Today, poverty cuts crop yields by a factor of 10,” Tol noted. “By contrast, climate change in 50 years would cut yields by factor of two.”

Regarding the global distribution of the climate problem, Tol rejected the Pope’s claim that poor countries are especially vulnerable to climate change primarily “because of where they are.” Tol countered that these countries are more vulnerable to the effects of climate change primarily “because they are poor,” citing their inability to adapt and their reliance on agriculture.

Lea defended the two-degree target, arguing that it has pushed countries to pursue their own domestic climate policies even if those policies do not yet add up. Now that we are likely to cross that threshold, Lea suggested, “climate science should work very hard to define the temperature thresholds for the tipping points” associated with climate warming, such as melting ice fields and degrading coral reefs, which he estimates to range from 1.5 degrees to 4 degrees.

Jesse Jenkins asked Wigley and Tol to reconcile their views. Wigley replied that he agreed with Tol that between now and 2100 the impact of warming may be modest, but that larger impacts were likely over the long-term and would disproportionately affect the poor.

“But even if we lose the Greenland ice sheet,” responded Tol, “resulting in a 10 to 12 meter sea level rise — which is enormous — it would happen by the end of the millennium, not by the end of century.”

Lea and Wigley both agreed that these climate impacts would occur over centuries.

Geden argued that the strict adherence to the two-degree target has led to a politicization of the science.

“We end up not with evidence based policy-making but policy based evidence-making. The policy solutions aren't designed from the problems,” Geden argued. “The problems are instead constructed to fit to the preferred solutions.”

Geden was also concerned that a strict focus on staying under the two-degree limit will very soon impel to a turn to geoengineering strategies, which will “only address the temperature problem” and not other related problems such as ocean acidification. After Paris, Geden hopes, climate negotiations will become more serious by becoming “more pragmatic, focussing on specific areas and concrete specific actions with immediate benefits.”

A general sense from the panel was that climate change will not be fixed once and for all with an international agreement. As environmental journalist Andrew Revkin remarked, climate change seems to be a grand challenge that needs to be worked on “year after year” and that we need to “normalize climate policy” and “apply best practices,” similar to society’s approaches to public health and poverty alleviation. Jane Long commented that “we can only control emissions,” so that should be the focus of climate policy. Tol added two words: “We can only control our own emissions.”