Climate Q&A

If carbon dioxide hits a new high every year, why isn't every year hotter than the last?

Rebecca Lindsey | May 29, 2025

Thanks to the global oceans, Earth's surface temperature doesn't react instantly to the full impact of a climate disturbance. That delayed reaction has pros and cons.

What's the hottest Earth has been "lately"?

Michon Scott | March 05, 2025

Natural variability can explain much of Earth's average temperature variation since the end of the last ice age, but over the past century, global average temperature has risen from near the coldest to the warmest levels in the past 11,300 years.

What's the hottest Earth's ever been?

Michon Scott | February 26, 2025

Earth’s hottest periods occurred before humans existed. Those ancient climates would have been like nothing our species has ever seen.

Does it matter how much the United States reduces its carbon dioxide emissions if China doesn't do the same?

Michon Scott | August 30, 2023

China has overtaken the U.S. as the largest annual emitter, but all countries have to reduce their emissions if we want to stop further global warming. Every fraction of a degree of warming we avoid lowers the risks to people and other life on Earth.

How do we know the build-up of carbon dioxide in the atmosphere is caused by humans?

Rebecca Lindsey | October 12, 2022

Fossil fuels are the only source of carbon dioxide large enough to raise atmospheric carbon dioxide amounts so high so quickly.

If the globe is still warming, then why are some locations not warming while others have experienced cooling?

David Herring | October 12, 2022

Differences in exposure to sunlight, cloud cover, atmospheric circulation patterns, and other factors influence whether and how much a location is warming or cooling.

Can we slow or even reverse global warming?

David Herring | October 12, 2022

While we cannot stop global warming overnight, or even over the next several decades, we can slow the rate and limit the amount of global warming by reducing human emissions of heat-trapping gases and soot.

What evidence exists that Earth is warming and that humans are the main cause?

David Herring | October 12, 2022

There is overwhelming scientific evidence that Earth is warming and a preponderance of scientific evidence that human activities are the main cause.

What's the coldest the Earth's ever been?

Michon Scott | February 18, 2021

Our planet’s history includes episodes of cold so extreme that glaciers reached sea level in equatorial regions.

Does "global warming" mean it's warming everywhere?

Caitlyn Kennedy | October 29, 2020

It’s only when we “zoom out” to the planet-wide scale that trends in surface temperature are obvious: despite a few, rare areas experiencing cooling, the vast majority of places across the globe are warming.

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Climate Q&A