Letter: Slowing global warming also requires action on super-pollutants

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

An example is the shrinking reflective sea ice shield in the Arctic. If we lose all of that, which could happen in 10 to 15 years, we’ll add 25 years’ worth of climate emissions and exceed the 1.5°C and 2°C targets. This will collapse the permafrost and trigger a waterfall that could be unstoppable.

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

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

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

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

Durwood Zaelke
President, Institute for Governance and Sustainable Development
Assistant Professor, University of California, Santa Barbara, California, USA

Teresa H. Sadler