SOURCE: The Economist

DATE: November 16, 2017

SNIP: The Paris agreement assumes, in effect, that the world will find ways to suck CO2 out of the air. That is because, in any realistic scenario, emissions cannot be cut fast enough to keep the total stock of greenhouse gases sufficiently small to limit the rise in temperature successfully. But there is barely any public discussion of how to bring about the extra “negative emissions” needed to reduce the stock of CO2 (and even less about the more radical idea of lowering the temperature by blocking out sunlight). Unless that changes, the promise of limiting the harm of climate change is almost certain to be broken.

Fully 101 of the 116 models the Intergovernmental Panel on Climate Change uses to chart what lies ahead assume that carbon will be taken out of the air in order for the world to have a good chance of meeting the 2°C target. The total amount of CO2 to be soaked up by 2100 could be a staggering 810bn tonnes, as much as the world’s economy produces in 20 years at today’s rate. Putting in place carbon-removal schemes of this magnitude would be an epic endeavour even if tried-and-tested techniques existed.

They do not.

[F]acing the shortcomings of Paris is beyond most governments. Under Mr Trump, America is not prepared to reduce the flow of emissions, let alone the stock. But the problem would not magically be solved even if America returned to the fold. Many rich countries say they are already doing their bit by cutting emissions more steeply than developing countries. In fact, taking carbon dioxide from the atmosphere is not an alternative to belching out less greenhouse gas. It is necessary in its own right. Unless policymakers take negative emissions seriously, the promises of Paris will ring ever more hollow.