Global Warming is defined as the increase of the average temperature on Earth. As the Earth is getting hotter, disasters like hurricanes, droughts and floods.
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Over the last 100 years, the average temperature of the air near the Earth´s surface has risen a little less than 1° Celsius (0.74 ± 0.18°C, or 1.3 ± 0.32° Fahrenheit). Does not seem all that much? It is responsible for the conspicuous increase in storms, floods and raging forest fires we have seen in the last ten years, though, 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. Out of the 20 warmest years on record, 19 have occurred since 1980. The three hottest years ever observed have all occurred in the last ten years, even.
Earth should be in cool-down-period
But it is not only 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 100,000years.
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What Is The Greenhouse Effect?
Seen from space, our atmosphere is but a tiny layer of gas around a huge bulky planet. But it is this gaseous outer ring and its misleadingly called greenhouse effect that makes life on Earth possible – and that could destroy life as we know it.
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The sun is the Earth’s primary energy source, a burning star so hot that we can feel its heat from over 150 million kilometers away. Its rays enter our atmosphere and shower upon on our planet. About one third of this solar energy is reflected back into the universe by shimmering glaciers, water and other bright surfaces. Two thirds, however, are absorbed by the Earth, thus warming land, oceans, and atmosphere.
Much of this heat radiates back out into space, but some of it is stored in the atmosphere. This process is called the greenhouse effect. Without it, the Earth’s average temperature would be a chilling -18 degrees Celsius, even despite the sun’s constant energy supply.
In a world like this, life on Earth would probably have never emerged from the sea. Thanks to the greenhouse effect, however, heat emitted from the Earth is trapped in the atmosphere, providing us with a comfortable average temperature of 14 degrees.
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So, how does it work? Sunrays enter the glass roof and walls of a greenhouse. But once they heat up the ground, which, in turn, heats up the air inside the greenhouse, the glass panels trap that warm air and temperatures increase.
Our planet, however, has no glass walls; the only thing that comes close to acting as such is our atmosphere. But in here, processes are way more complicated than in a real greenhouse.
Like a radiator in space
Only about half of all solar energy that reaches the Earth is infrared radiation and causes immediate warming when passing the atmosphere. The other half is of a higher frequency, and only translates into heat once it hits Earth and is later reflected back into space as waves of infrared radiation.
This transformation of solar radiation in to infrared radiation is crucial, because infrared radiation can be absorbed by the atmosphere. So, on a cold and clear night for example, parts of this infrared radiation that would normally dissipate into space get caught up in the Earth’s atmosphere. And like a radiator in the middle of a room, our atmosphere radiates this heat into all directions.
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A temperature rise as fast as the one we have seen over the last 30 years has never happened before, as far as scientists can ascertain. Moreover, normally the Earth should now be in a cool-down-period, according to natural effects like solar cycles and volcano activity, not in a heating-up phase.
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What Will The Climate Be Like in 2100?
Stanford University climatologist Stephen Schneider discusses what we know and don’t know about the future of the Earth’s climate, and whether it is worth spending trillions of dollars to fight climate change.
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Stephen Schneider, Climatologist, Stanford University
"How do we know if people are going to take this problem seriously?" (Photo courtesy: Stephen Schneider)
Stephen Schneider, Climatologist, Stanford University"How do we know if people are going to take this problem seriously?" (Photo courtesy: Stephen Schneider)
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What will the Earth's climate be like at the end of this century?
What's the old joke? Prediction is hard, especially about the future. What do you have to do to predict the climate of 2100? Well, you have to know how much CO2, methane, nitrous oxide, aerosols - that's dust and smoke - are going to be there, because that changes what we call the forcing - the pressures on the climate system - to be warmer or colder. We know it's going to be warmer. That's virtually certain.
But you don't know what those are going to be on the basis of any history. There's never been a time before when there was six to ten billion people on the Earth, when they're demanding dramatic increases in their standards of living, and when they're using the cheapest available technology - usually coal and oil burning, big cars - to get there. So, before you can forecast how warm it will be in 2100 - and whether it's worth a trillion-dollar investment not to have that outcome - you've got to know a bunch of social factors.
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