Photo Illustration by Andrea D'Aquino
How do we know climate change is really happening?
Climate change is often cast as a prediction made by complicated computer models. But the scientific basis for climate change is much broader, and models are actually only one part of it (and, for what it’s worth, they’re surprisingly accurate).
For more than a century, scientists have understood the basic physics behind why greenhouse gases like carbon dioxide cause warming. These gases make up just a small fraction of the atmosphere but exert outsized control on Earth’s climate by trapping some of the planet’s heat before it escapes into space. This greenhouse effect is important: It’s why a planet so far from the sun has liquid water and life!
<aside> 🔥 However, during the Industrial Revolution, people started burning coal and other fossil fuels to power factories, smelters and steam engines, which added more greenhouse gases to the atmosphere. Ever since, human activities have been heating the planet.
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We know this is true thanks to an overwhelming body of evidence that begins with temperature measurements taken at weather stations and on ships starting in the mid-1800s. Later, scientists began tracking surface temperatures with satellites and looking for clues about climate change in geologic records. Together, these data all tell the same story: Earth is getting hotter.
Source: NASA Goddard Institute for Space Studies | By Veronica Penney
Average global temperatures have increased by 2.2 degrees Fahrenheit, or 1.2 degrees Celsius, since 1880, with the greatest changes happening in the late 20th century. Land areas have warmed more than the sea surface and the Arctic has warmed the most — by more than 4 degrees Fahrenheit just since the 1960s. Temperature extremes have also shifted. In the United States, daily record highs now outnumber record lows two-to-one.
We also know that climate change is happening because we see the effects everywhere. Ice sheets and glaciers are shrinking while sea levels are rising. Arctic sea ice is disappearing. In the spring, snow melts sooner and plants flower earlier. Animals are moving to higher elevations and latitudes to find cooler conditions. And droughts, floods and wildfires have all gotten more extreme. Models predicted many of these changes, but observations show they are now coming to pass.
How bad are the effects of climate change going to be?
It depends on how aggressively we act to address climate change. If we continue with business as usual, by the end of the century, it will be too hot to go outside during heat waves in the Middle East and South Asia. Droughts will grip Central America, the Mediterranean, and southern Africa. And many island nations and low-lying areas, from Texas to Bangladesh, will be overtaken by rising seas.
Conversely, climate change could bring welcome warming and extended growing seasons to the upper Midwest, Canada, the Nordic countries and Russia. Farther north, however, the loss of snow, ice and permafrost will upend the traditions of Indigenous peoples and threaten infrastructure.
What will it cost to do something about climate change, versus doing nothing?
One of the most common arguments against taking aggressive action to combat climate change is that doing so will kill jobs and cripple the economy. But that implies that there’s an alternative in which we pay nothing for climate change. And unfortunately, there isn’t.
<aside> 🔥 In reality, not tackling climate change will cost a lot and will cause enormous human suffering and ecological damage, while transitioning to a greener economy would benefit many people and ecosystems around the world.
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