Mitigation centers on the root cause of climate change: the heat-trapping greenhouse gases humans are adding to the atmosphere faster than our planet can absorb them. These can be addressed by reducing the sources of greenhouse gas emissions, or enhancing “sinks” of greenhouse gases that remove them from the atmosphere.
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​Reducing sources: Almost three-quarters of humans’ greenhouse gas emissions come from burning fossil fuels like coal, oil and natural gas, (2) so mitigation often focuses on replacing those fuels with other sources of energy, like renewables and nuclear power. Mitigation can also tackle other sources of greenhouse gases: protecting forests from being cut down, for instance, or collecting methane from landfills.
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​Enhancing sinks: Other forms of mitigation, like growing new forests and designing and building “direct air capture” systems, work by taking greenhouse gases out of the atmosphere—sometimes called “carbon removal.” These approaches are challenging to do at a very large scale, and they do not eliminate the need to drastically lower our emissions. Still, authorities like the Intergovernmental Panel on Climate Change agree that some carbon removal will be needed to head off the worst climate change scenarios (3).

If mitigation is successful worldwide, then one day greenhouse gases will stop building up in the atmosphere, and the planet will slowly stop warming. Even so, we will already have created a hotter world, changed the Earth’s weather patterns, and “locked in” some future changes—like sea level rise, which may continue for hundreds of years after the Earth’s temperature stabilizes.
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Adaptation to these changes will vary from place to place. Often, it involves building or retrofitting infrastructure, like a better storm drain system to manage increased flooding. But adaptation can also include natural solutions, like restoring wetlands to buffer hurricanes, or behavior and policy changes, like growing new food crops that can better handle warmer seasons and droughts.
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Ideally, adaptation is proactive, building systems to withstand not only current but future climate change. In Bangladesh, one of the most vulnerable countries in the world to sea level rise and saltwater intrusion, the port city of Mongla is investing in embankments, drainage, flood-control gates and water treatment to get ahead of rising waters, and economic development to provide refuge and work opportunities for thousands of people displaced from nearby towns. Areas that don’t take early steps like these will find themselves adapting reactively: rebuilding after climate change has already destroyed buildings, forced people from their homes, and taken livelihoods and lives.

The final aim of mitigation is to stop the buildup of greenhouse gases in the atmosphere altogether, and begin drawing them down. The Paris Agreement of 2015 set worldwide targets for mitigation, with almost every country on Earth agreeing to zero out their greenhouse gas emissions in time to halt global warming at no more than 2° C, and ideally at no more than 1.5° C.
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Today, however, mitigation is not on track to meet either of these goals.4 In fact, despite ambitious pledges and fast progress in sectors like clean electricity, greenhouse gas emissions are still rising worldwide.
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Failure to mitigate climate change will only make it more important to adapt. So far, however, policymakers have not kept up with this urgent need. Most funding to deal with climate change worldwide has been spent on mitigation, with only a small share given to adaptation, (5) and the United Nations estimates that the need for adaptation is growing faster than the spending on it (6).
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While all countries will need to both mitigate and adapt to climate change, some have far more resources to do so than others. Without financial and technological aid, low- and middle-income countries are unlikely to adapt quickly enough to save their people from serious hardship. In the Paris Agreement, wealthy developed nations pledged to give $100 billion a year to developing nations to help with mitigation and adaptation, but have so far fallen short of that pledge.
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A renewed commitment to mitigation and adaptation today will be well worth the investment. The sooner the world stops the rise of greenhouse gases, and shields people from the warming we have already caused, the less we will ultimately have to spend to stabilize our climate, and the more lives and livelihoods we will save along the way.

Published December 14, 2023

FOOTNOTES

1 The Intergovernmental Panel on Climate Change uses the following definitions. Mitigation: “A human intervention to reduce emissions or enhance the sinks of greenhouse gases.” Adaptation: “In human systems, the process of adjustment to actual or expected climate and its effects, in order to moderate harm or exploit beneficial opportunities. In natural systems, the process of adjustment to actual climate and its effects; human intervention may facilitate adjustment to expected climate and its effects.” Intergovernmental Panel on Climate Change: “Special Report: Global Warming of 1.5° C: Glossary.” 2018.

2 Climate Watch and World Resources Institute: “Historical Greenhouse Gas Emissions.” Data is for 2020 (the most recent year available).

3 Intergovernmental Panel on Climate Change: "Mitigation pathways compatible with long-term goals." In IPCC, 2022: . Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. doi:10.1017/9781009157926.005.

4 Intergovernmental Panel on Climate Change: “Summary for Policymakers.” In “Climate Change 2023: Synthesis Report,” 2023. A.4: Current Mitigation Progress, Gaps and Challenges.

5 Intergovernmental Panel on Climate Change: “Summary for Policymakers.” In “Climate Change 2023: Synthesis Report,” 2023. A.3: Current Progress in Adaptation and Gaps and Challenges.

6 United Nations Environment Programme: “Adaptation Gap Report 2022,” November 1, 2022.