Warmer conditions are having an impact on our planet. The world's surface air temperature warmed 0.6° C (1.1°F) on average during the last century. This may not sound like very much change, but it is. Below are some effects of climate change that are happening today.
More Ocean and Less Ice
Rising sea level is a threat to coastal communities, wetlands, and coral reefs. During the 20th Century, sea level rose about 15 cm (6 inches). In part this was because of melting glaciers. The water from the melted ice is added to streams and rivers and eventually makes its way to the ocean. Over the past 100 years mountain glaciers, Arctic glaciers, and Greenland’s ice have decreased dramatically in size. Sea level rise is also happening because as water warms, it takes up more space – it expands larger. Models predict that sea level may rise as much as 59 cm (23 inches) during the 21st Century – four times the amount of sea level rise we’ve seen in the past century.
Warmer waters in the shallow oceans have contributed to the death of about a quarter of the world's coral reefs in the last few decades. Many of the coral animals died after weakened by coral bleaching a process tied directly to warmed waters. Also, corals and other marine life find it more difficult to grow their shells and bones as seawater takes in for carbon dioxide from the atmosphere and becomes more acidic.
Each year, the amount of sea ice that covers the Arctic Ocean grows in the winter and then melts at its edges in the summer. But lately, warmer temperatures have caused more ice to melt in the summer and less ice to grow in winter. The summer thickness of sea ice is about half of what it was in 1950. Melting sea ice could cause changes in ocean circulation as the temperature and density of water changes. It is also speeding up warming in the Arctic – with less ice, less sunlight is reflected out to space and more is absorbed by the water and land.
Changing Climate Means Changing Weather
Climate warming is causing changes to weather in different regions of the world. In particular, it is causing more extreme weather events than we have seen in the past. These extreme weather events can have impacts on human health, limiting access to clean drinking water, food, and shelter and taxing people’s ability to cope with heat, drought or flood.
- More rain and flooding. Warmer temperatures have led to more intense rainfall events in some areas. This can cause flooding – a risk to the environment and human health.
- More extreme drought. Warmer temperatures cause more evaporation, turning water into vapor in the air, and causing drought in some areas of the world. Places prone to drought are expected to become even drier over the next century. This is bad news for farmers who can expect fewer crops in these conditions.
- Stronger hurricanes. There is evidence that the number of intense hurricanes has increased in the Atlantic since 1970. This may also be true for tropical cyclones in other parts of the world. Scientists continue to study whether climate is the cause.
- Heat waves. It is likely that heat waves have become more common in more areas of the world.
According to computer models, more global warming is in our future. If we continue to emit as many, or more, greenhouse gases, this will cause much more warming during the 21st Century than we saw in the 20th Century. During the 21st Century, various computer models predict average temperatures will climb 1.8°-4.0°C (3.2°-7.2°F).