Planet Earth's nine lives: Our planet's limits

Climate change: the planet is heating up and could soon do so much faster

You probably know a good deal about climate change, especially if you've read my guide. Climate change is often called 'global warming' which gives the impression that everywhere on the planet is getting hotter. This isn't quite true. Overall, our planet is heating up, but some parts - like the polar regions What are the polar regions?You knew this, didn't you!? The Arctic and Antarctic, the icy parts at the top and bottom of the planet are the polar regions. The Arctic is warming particularly fast - are warming much faster than others.

Sometimes changing weather systems can channel cold air away from the Arctic, giving other parts, like northern Europe or eastern North America, very cold winters. People get mixed up thinking that a cold winter means the climate is getting colder, not warmer. So you often hear people say, "I don't believe in global warming. This winter is so cold. Global warming is a big hoax." That sort of stuff. You can see why they say it, but it really just shows that they don't understand (or don't want to know about) what climate change means. There's all kinds of scientific evidence which shows without doubt that the planet as a whole is getting hotter.

We know why the climate is changing. It's because humans burn gigantic amounts of carbon-based fossil fuels: coal, oil and natural gas. Burning these produces energy for industry (like electric power stations) and transport (cars, trucks, planes, ships). Most of the waste gasesCarbon capture and storageThere are plans to capture and store some of these waste gases but it's only happening on a very small scale. It's going to be very expensive plus there are other problems. Best not to burn carbon fuels in the first place! from this burning are made up of carbon dioxide (CO2) and go straight into the air.

CO2 is the main greenhouse gas. Without it the planet would freeze, because it acts like a blanket, trapping some of the sun's heat in our atmosphere. So too much CO2 is bad because it's like piling on too many blankets. And there is already too much. CO2 levels have shot up by one third in just 200 yearsThat is from the start of the Industrial Revolution, which is when people started burning coal big time. Today it's rising faster than ever, as more people use more and more energy.

There are many other greenhouse gases which human industry and farming produce, often by accident. The best known of these is methane, which is around 25 times more powerful than CO2 in its warming effects.

Scientists know that natural systems like climate tend to change quite suddenly from one stable state to another. We've been very lucky since the end of the last ice age (about 11,500 years ago) because the climate has been quite stableThis period of time is known as the Holocene. Some scientists suggest we are now entering a new period called the Anthropocene: a period in which the climate is now becoming unstable due to human influence. 'Anthropo' means 'people' so anthropology means the study of people: just right for humans (and penguins too). But the extra burden of greenhouse gases that people are unintentionally pumping into the atmosphere is 'forcing' the climate towards another, hotter, stable state.

This is happening more rapidly than expected because of something called feedback. One important example of feedback is happening right now in the Arctic. Until recently, the Arctic Ocean has been mostly covered by a blanket of floating ice. This ice, being white, reflects almost all the sun's heat back into space. When it melts away, we are left with dark ocean waters which, because they are so dark, absorb most of the sun's heatThe albedo effectHave you noticed that if you leave something black in the sun, it gets much hotter than something white. It's the same with dark ocean waters: they absorb far more heat from the sun than they would if covered in white reflective ice. This is the albedo effect.. So the water gets warmer and more ice melts, so the water gets warmer still. And because the warmer water is exposed to the air, some of it evaporates as water vapour, which is itself a powerful greenhouse gas. So warming increases yet more. This is another feedback.

Tackling climate change: Right now, climate change is the most important planetary boundary because we're already over the limit for CO2. The limit the scientists suggest is 350 parts per millionMeasuring greenhouse gases350 parts per million (shortened to 'ppm') sounds very small. It is just 0.035 percent but in the case of CO2 is critically important of CO2 in the air. It's just passed 400ppm (September 2014) and continues upwards faster than ever . There are two ways people can fix this. The best way would be to quit using fossil fuels almost totally. This is unlikely to happen fast enough even though world nations are coming together regularlyUnited Nations' climate conferencesThese conferences, called COPs ('Conferences of the Parties') are arranged by the United Nations Framework Convention on Climate Change or UNFCCC. They try to get countries to agree to big cuts in greenhouse gases. This is proving very difficult! to try to find ways to do it. But, like it or not (and the ‘greens’ definitely don't!), there are alternative ways to bring down greenhouse gas levels in the air:

• Generate electric power using a mix of renewables like wind, solar and nuclear power. [more on this]

• Geoengineering is a big topic [more] and there are many reasons why some schemes might neither work nor be a good idea. Environmentalists ('greens') don't like it, partly because they (probably rightly) think that once people start using it, the pressure to solve the real problem - burning too much fossil fuel - will be forgotten. Geoengineering could seem an easy option to avoid having to stop using fossil fuels. Though really, it's a sort of emergency toolbox for people to use if things get desperate. So it makes good sense that scientists are already doing lots of experiments to find out what could work and how safe and easy it is to do.

Humans are the cleverest creature to have ever lived on planet Earth. You can fix climate change, the biggest problem of all. You just have to agree to all pull together and do what needs to be done. And there's a bonus: if climate change really is sorted, several of the other nine planetary boundaries will also be largely sorted too. But single countries can't do this on their own. The whole world needs to unite and agree how to fix it and then do it! This happened successfully with the ozone treatyI'll be looking at this later in the guide. And in December 2015 at a huge meeting of the the leaders of the world's nations in Paris (France), everyone agreed on a fair deal to tackle climate change. Unfortunately, the USA — one of the world's biggest polluters — now wants to pull out of the deal (June 2017). But they are on their own since the rest of the world is determined to stick with the agreement. More on this...