The greatest risk of near-term temperature increases, covered by Leslie Hook’s article “World on course to pass critical 1.5C warming threshold within five years” (Report, May 10), is from self-reinforcing feedback loops — where the planet starts to warm itself outside of human influence — and pushes the climate past irreversible tipping points. By crossing the temperature targets set in the Paris agreement, we significantly increase the risk of runaway warming.

An example is the shrinking shield of reflective sea ice in the Arctic. Should we lose all of it, which could happen in 10 to 15 years, we’ll add the equivalent of 25 years of climate emissions and blow right past the 1.5C and 2C targets. This will collapse the permafrost and set off a cascade that may be unstoppable.

Another example is the melting of the Greenland ice sheet, which early warning signs suggest is close to a tipping point, with the best estimate around 1.6C for the threshold for irreversible melting. And while it may take hundreds of years to see the full extent of the resulting sea-level rise, sooner or later we’ll see 5-7 metres as the Greenland ice sheet disintegrates.

This is not the future we want to face and Hook is right to remind us how little time we have to avert it.

The best and only way to limit warming fast enough to slow feedbacks is to cut the shortlived super climate pollutants, especially methane, but also black carbon and hydrofluorocarbon (HFC) refrigerants, which is the only way we know to slow near-term warming as we shift to clean energy and decarbonise by 2050.

We need to complement fossil fuel-focused climate mitigation strategies with strategies targeting methane and the other largely neglected climate super-pollutants to limit warming over the crucial next two decades before it is too late.

Durwood Zaelke
President, Institute for Governance & Sustainable Development
Adjunct Professor, University of California Santa Barbara, CA, US