Greenhouse gases have far-ranging environmental and health effects. They cause climate change by trapping heat, and they also contribute to respiratory disease from smog and air pollution. Extreme weather, food supply disruptions, and increased wildfires are other effects of climate change caused by greenhouse gases. The typical weather patterns we’ve grown to expect will change; some species will disappear; others will migrate or grow.

How to reduce greenhouse gas emissions

Virtually every sector of the global economy, from manufacturing to agriculture to transportation to power production, contributes greenhouse gases to the atmosphere, so all of them must evolve away from fossil fuels if we are to avoid the worst effects of climate change. Countries around the world acknowledged this reality with the Paris Climate Agreement of 2015. The changes will be most important among the biggest emitters: Twenty countries are responsible for at least three-quarters of the world’s greenhouse gas emissions, with China, the United States, and India leading the way.

The technologies for ramping down greenhouse gas emissions already exist, for the most part. They include swapping fossil fuels for renewable sources, boosting energy efficiency, and discouraging carbon emissions by putting a price on them. (Read more about such solutions here.)

The world technically has only one-fifth of its “carbon budget” — the total is 2.8 trillion metric tons — remaining in order to avoid warming the Earth more than 1.5 degrees Celsius. Halting the trends in motion will require more than just phasing out fossil fuels. In fact, the paths to halting global temperature increase of 1.5 or 2 degrees C, the two goals outlined by the IPCC, rely in some way on adopting methods of sucking CO2 from the sky. Those include planting trees, conserving existing forests and grasslands, and capturing CO2 from power plants and factories.