What is global warming?

Global warming is defined as the increase of the average temperature on Earth. And as temperatures increase, so do natural disasters.
A UN global warming scenario predicts temparature increases of up to six or seven degress Celsius. / Credits: Reuters

Over the last 100 years, the average air temperature near the Earth’s surface has risen by a little less than 1 degree Celsius, or 1.3 degrees Fahrenheit. Doesn't seem that much, does it? Yet this warming is at least partly responsible for the conspicuous increase in storms, floods and raging forest fires we have seen in recent years, say scientists.

Their data show that an increase of one degree Celsius makes the Earth warmer now than it has been for at least a thousand years.The top 11 warmest years on record were all in the previous 13 years, said NASA in 2007, and the first half of 2010 went down in history as the hottest ever recorded.

Projections from the UN climate change body the Intergovernmental Panel on Climate Change (IPCC) say that global surface temperature will probably rise a further 1.5 to 4.8  degrees Celsius during the 21st century.

That huge range of estimates is due to the amazing complexity of our Earth’s climate system and the uncertainty about whether mankind will fight this warming or continue with business-as-usual.

A certain degree of warming is unavoidable even if we managed to reduce our carbon emissions immediately. Oceans, for example, act as huge heat repositories that follow changes in air temperature with a time lag of decades or even hundreds of years. Melting ice caps reflect less sunlight than previously, so our planet absorbs more and more heat.

Exactly how these changes will influence the warming trend is unclear. All we know for certain is that it’s going to be warmer and that human greenhouse gas emissions are an important reason for this.

Are climate change and global warming one and the same?

In a nutshell: global warming is the cause, climate change is the effect.

Scientists often prefer to speak about climate change instead of global warming, because higher global temperatures don’t necessarily mean that it will be warmer at any given time at every location on Earth.

Warming is strongest at the Earth's Poles, the Arctic and the Antarctic, and will continue to be so. In recent years, fall air temperatures in the Arctic have been at a record 9 degrees Fahrenheit (5 degrees Celsius) above normal, according to the U.S. National Oceanic and Atmospheric Administration.

But changing wind patterns could mean that a warming Arctic, for example, leads to colder winters in continental Europe. Regional climates will change as well, but in very different ways. Some regions like parts of Northern Europe or West Africa will probably get wetter, while other regions like the Mediterranean or Central Africa will most likely receive less rainfall.

But it is not just about how much the Earth is warming, it is also about how fast it is warming. There have always been natural climate changes—Ice Ages and the warm intermediate times between them—but those evolved over periods of 50,000 to 100,000 years.

In the past, climate change was triggered by changes in the sun’s energy output, the changing position of continental plates, or the rotating axis of the Earth itself. Many plants and animals were able to adapt to these slowly changing climates. Even humans have changed their habitat according to the comings and goings of glaciers.

All these so-called natural forcings, however, have been ruled out as causes for the warming visible in the last 30 years. Since 1980, temperatures have risen faster than ever before, as far as scientists can ascertain.

This radical change is leading towards a sudden loss of biodiversity—a dwindling number and variety of plants and animals. Many species simply won’t be able to adapt fast enough. According to the most recent UN assessment, 20 to 30 percent of the Earth's plant and animal species face extinction if the world warms by between 1.5 and 2.5 degrees Celsius.

Even for humans, climate change won’t be a smooth transition to a warmer world, warns the Tipping Points Report by Allianz and WWF. Twelve regions around the world could be especially affected by abrupt changes, among them the North Pole, the Amazon rainforest, and California.

All these facts lead scientists to infer that the global warming we now experience is not a natural occurrence and that it is not brought on by natural causes. They say that responsibility lies with humanity’s carbon emissions.

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