What could the effects of climate change be?


Scientists now believe that the Earth could warm up by as much as 3.9ºC (7ºF), on average, by the end of the century, if emissions of greenhouse gases continue to grow at current rates. That could trigger all sorts of big changes in the environment.

To start with, scientists expect sea level to rise by three feet or more — partly because water expands as it warms, partly due to melting ice in Greenland and other places. Low-lying areas — significant parts of states like Florida, and entire countries like Bangladesh and the Maldives will be more prone to erosion and to catastrophic flooding.

The warming could also make the most powerful of tropical storms even more powerful. And rainstorms in general are likely to become more intense, with more of them causing damaging floods.

As mountain glaciers melt, they will cause even more flooding — at first. But if they shrink enough, the fresh water they provide will become scarce. Billions of people in India and China, for example, depend on water that comes off glaciers in the Himalayas and the Tibetan Plateau. In the US, earlier snowmelt in the Rocky and Sierra Nevada mountains will mean less meltwater for a thirsty California during the summer when it is really needed.

In already arid regions like Australia and the American West, droughts are likely to come more often and be more severe. That is likely to lead to more wildfires. Heat waves will be more frequent too, in temperate zones, including most of the continental US.

All of these changes would affect people’s comfort and their physical safety. But they could have an even greater impact on other species. Plants and animals thrive in specific climate conditions and cannot easily adapt to rapid changes.

The trees that produce Vermont maple syrup, for example, may have trouble surviving in Vermont as the New England climate changes, and Georgia may lose its population of Brown Thrashers — the state bird.

The warming of the oceans has already contributed to a worldwide die-off in coral reefs, which is expected to accelerate. Corals are home to a wide variety of sea-dwelling creatures, so when they go, many other species could be in big trouble — including the fish people in places like the Philippines depend on for income and for food.

If we cut back drastically on greenhouse gases, we can limit how high the temperature will go. But if not, these changes will continue to happen—and the further they go, the harder they’ll be to reverse.

How do we know?

We know ice is disappearing into the sea thanks in part to a pair of satellites. Collectively called GRACE, their separation changes slightly as they pass over areas of higher and lower gravity, representing higher and lower mass. Over time, they’ve seen Greenland getting less massive as it loses old ice faster than it is gaining new ice.