One point five—as in average global warming of no more than 1.5oC/2.7oF above pre-industrial levels—is fast becoming a rallying cry for many activists at the United Nations climate summit in Paris. “A moral imperative” was the phrase that ECO, a daily onsite newsletter produced by the Climate Action Network, used on Saturday.

“Countries questioning the urgent need to include a long-term goal to keep temperatures below 1.5°C,” CAN wrote, “should check their conscience.” ECO characterized the summit’s refusal so far to budge from the 2009 consensus view that the limit of tolerable global warming is 2ºC/3.6ºF as “a violation of the right to life of many human beings [that] threatens the existence of ecosystems and species.”
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CAN’s alarm is supported by the results of two years of consultation by scientists and other experts from more than 70 nations who criticized the 2ºC “guardrail” earlier this year as “inadequate.” Achieving a lower increase in warming would demand a much more aggressive transition away from carbon than conventional observers currently contemplate, possibly including so-called ‘negative emissions’ techniques to remove carbon dioxide from the atmosphere.
Nonetheless, the Philippines, Bangladesh, and nearly a score of other vulnerable states immediately called for the global temperature target to be lowered.
Their call is catching on in Paris, but stay tuned to see how the urgency is reflected in the final text.