This is the do-or-die decade for climate change, world scientists warn

Time’s up, according to the world’s scientists who have just issued their starkest warning yet with the release of a climate science report for the United Nation’s Intergovernmental Panel on Climate Change (IPCC).

The report released Monday is the first instalment of the IPCC’s Sixth Assessment Report (AR6), which will be finished in 2022. This installment, from Working Group 1, tackles the physical science basis of climate change. The report describes how little time is left to hit the brakes on warming and put the world on track to keep from breaching the 1.5 degrees Celsius threshold above pre-industrial temperature that scientists calculate can still keep the climate relatively safe. At a minimum, it is essential that we slow warming fast enough to keep the 1.5-degree target within sight, even with limited overshoot.

AR6 makes it clear that climate change is accelerating, and that every additional increment of climate pollution is causing irreversible harm. The record-shattering heatwaves and floods of the past month will become more and more frequent unless we slow the rate of warming.  We’re seeing self-reinforcing feedbacks starting to accelerate warming, and learning that we’re closer to crossing climate tipping points than previously thought. This includes news this week of weakening vital signs in the ocean’s heat conveyor belt, the Atlantic Meridional Overturning Circulation, with serious implications for sea-level rise along the Eastern United States, extreme weather shifts in Europe, and disruption of seasonal monsoons.

Tipping points are notoriously hard to quantify, and hence frequently excluded from climate models. But the probability — the fat-tail risk — is increasing every day that we’ll pass critical tipping points in a matter of years to decades.

In this do-or-die moment, the biggest immediate opportunity is to cut methane emissions, which also happens to be the fastest and probably cheapest way to slow warming. The landmark Global Methane Assessment by the United Nations Environment Programme and Climate and Clean Air Coalition calculates that reducing methane emissions by 45 percent by 2030 will avoid almost 0.3 degrees Celsius of warming globally and 0.5 degrees of warming in the vulnerable Arctic by the 2040s — while simultaneously preventing 255,000 premature human deaths every year, along with 775,000 asthma-related hospital visits, 73 billion hours of lost labour from extreme heat, and 26 million tonnes of crop losses globally.

While this UN methane report was published after the January 2021 deadline for inclusion in this AR6 report, AR6 recognizes the importance of “strong, rapid and sustained reductions in [methane] emissions” to limit warming in the near-term, especially as decarbonization measures, essential for reducing CO2 emissions, will also result in removal of the cooling particles that come with burning coal and diesel, “unmasking” existing warming and cancelling the cooling benefits of CO2 reductions until around mid-century. 

Climate change is kicking down our door today in a way that it wasn’t when the IPCC released their last science assessment in 2013. We’ve delayed serious mitigation action so long that we’re now responding to a climate emergency. It should be clear that world leaders, businesses, and citizens need real-time assessments to motivate and direct mitigation and adaptation. We need only to look to the COVID-19 pandemic to see the value of real-time science to understand and respond to virus variants and the effectiveness of masks, therapies, and vaccines. 

This is the decade of action to bend not just the emissions curve, but more crucially the warming curve. Heat is the enemy we need to beat. World leaders are increasingly recognizing that this decade must achieve both immediate and drastic cuts to methane and other super climate pollutants, along with accelerated efforts to transition to clean energy and decarbonize our economies no later than 2050. 

In the history of war, failure can be summed up in two words, “too late” — too late to assess the strength of our enemy, too late to develop our fighting capabilities and too late to rally our allies.  This was the warning from U.S. General Douglas MacArthur at the approach of World War II.

Thanks to AR6, we’re not too late in assessing the strength of our enemy — an enemy that is growing stronger the longer we wait. Now we need to move with lightning speed to develop our capabilities to fight climate change, and rally our allies starting with the leaders of the major economies and all countries of the world to make the immediate and drastic cuts to methane that will put us in position to win the sprint to 2030, even as we’re also running the marathon to net-zero emissions by 2050, and learning to pull CO2 and other climate pollutants out of the atmosphere at scale.

Durwood Zaelke is president of the Institute for Governance & Sustainable Development (IGSD) in Washington, D.C. and Paris, as well as adjunct professor at the University of California, Santa Barbara. He is co-author of “Cut Super Climate Pollutants Now!: The Ozone Treaty’s Urgent Lessons for Speeding Up Climate Action” (2021).

Gabrielle Dreyfus, Ph.D., is senior scientist at IGSD and has been an adjunct professor at Georgetown University.

Both Zaelke and Dreyfus are peer reviewers for AR6.