What is Climate Change?

Climate Change is more than just a few degrees of warming; it’s changing water, food, transportation, wildlife, ecosystems and much more. This is why it’s important to understand what’s happening and what’s at stake – for ourselves, our children, our grandchildren and theirs.

Scientists know this from a vast body of evidence, including temperature records from weather stations and ships, tree rings, ice cores, satellite observations and other natural indicators. The basic picture, famously illustrated in 1998 as a “hockey stick” graph, shows how temperatures remained fairly flat for centuries (the shaft of the stick) and then began rising rapidly (the blade). This is what’s known as greenhouse warming.

The increase is largely due to our activities. Humans have burned billions of tons of fossil fuels, sending carbon dioxide and other greenhouse gases into the air. These gases trap the Earth’s heat, warming it from a cool, livable state to a warmer one that’s less habitable. The gases will remain in the atmosphere for many years, causing further warming and changing the way our world works.

Our warming is accelerating. Since 2000, global emissions of greenhouse gases have grown by more than 50 percent — and we’re on track to keep going in that direction. If we want to limit global warming to about 1.5 degrees Celsius, we must slash emissions by an unprecedented amount and quickly reorient our economies toward a low-carbon future.

Even so, scientists are not predicting the end of humanity or the planet. If we limit warming to 1.5 degrees Celsius, there will still be harms, but they may be less severe than those expected if the temperature rises higher.

The poor will suffer the most. Wealthier people have greater buffers — like the money to buy air-conditioners to keep them cool during hot weather and the means to pay energy bills, for example. They’re also more likely to have jobs that keep them outdoors, where they can work when the weather is good and be able to evacuate before or after extreme events. The world’s poorest countries — which have contributed the least to the problem — will be hit harder than others.

We’re nearing critical thresholds — called climate tipping points — that could irreversibly accelerate global warming and produce other harmful effects. These include the loss of Arctic permafrost, which acts as a giant freezer that stores carbon, and the rapid thawing of methane in the oceans. Each of these will trigger further impacts — called feedbacks — that amplify or diminish the initial warming. Taking action now may enable us to avoid passing these tipping points. The alternative is a very grim future.

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