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What are climate change and global warming?

Polar bears on iceberg

What is climate change?

Global warming doesn’t mean we’ll all just have warmer weather in future.

As the planet heats, climate patterns change. It’ll mean more extreme and unpredictable weather across the world – many places will be hotter, some wetter, others drier.

We know the planet has warmed by an average of nearly 1°C in the past century. That might not sound much, but on a global scale it’s a huge increase and it’s creating big problems for people and wildlife.

What causes climate change?

UK coal fired power station

Burning fossil fuels

Over the past 150 years, the world’s industrialised nations have changed the balance of the carbon cycle by burning huge amounts of fossil fuels (concentrated carbon such as coal, oil and gas)

Cattle rearing in the Amazon

Breeding cattle and cutting down forests

Industrialised nations have also breeding vast numbers of methane-producing livestock and cutting down the forests that naturally absorb carbon dioxide from the air.

Sunset behind clouds in Mexico

Trapped carbon dioxide

The extra carbon dioxide in the atmosphere traps more of the sun’s heat, so it’s been raising global temperatures. The speed of change has been faster than any natural process, and faster than many natural systems can adapt.

Find out about the effects of climate change.

How hot can it get?

A rise of just 2°c would mean:

  • severe storms and floods in some countries, droughts in many more
  • seas become more acidic, coral and krill die, food chains are destroyed
  • little or no Arctic sea ice in summer – not just bad news for polar bears, it also means that the global climate warms faster (as there’s less polar ice to deflect sunlight)

Iceberg in Antarctic

Beyond 2°c:

Scientists predict possible rises of up to 6°C this century if we don’t drastically cut greenhouse gas emissions.

It almost doesn’t bear thinking about what this would mean:

  • Rainforests dying.
  • Increased melting of the ancient ice sheets of Greenland and Antarctica.
  • Dramatic sea level rises.
  • And people and animals suffering along the way.
That’s why we must act now.

What the science is telling us

Some people might try to tell you that global warming is natural, or that the Earth is actually cooling. Or they might suggest there’s nothing we can do. But here’s what the science tells us:

A boat at sunset

Temperatures are rising faster than ever

The Earth’s climate has always changed: temperatures have risen and fallen over thousands of years. But it’s happening now at a far faster rate than ever before, which doesn’t give the world’s species (including ourselves) much time to react or adapt.

Cooling towers letting out steam and smoke at a coal-fired power station near Pontefract in Yorkshire, UK.

Man made global warming

The overwhelming evidence is that the global warming we’re seeing now is mostly man-made – it’s largely down to burning fossil fuels and large-scale deforestation. It’s not a natural process, no matter how much climate change deniers may claim it is.

The good news is that if we accept humans are a major cause of climate change, we can choose to do something about it. But we have to do it soon.

Global warming terms explained:

Low clouds over the River Danube flowing through the Iron Gate Gorge, Djerdap National Park, Serbia, June 2009.

Carbon dioxide (CO2)

Carbon dioxide is a natural gas. It’s essential for all life on Earth. It’s absorbed by plants as they grow, and emitted by all life forms when they respire and when they die (or when they’re burned as fuel). Other than water vapour, it’s the most common greenhouse gas.

Greenhouse effect graphic

Greenhouse gases

Greenhouse gases include carbon-based gases such as carbon dioxide and methane. They’re vital in the Earth’s atmosphere in certain quantities because they help trap and retain some of the sun’s heat (the ‘greenhouse effect’). This makes life as we know it possible on Earth – without it the world would be mostly frozen. But too much is dangerous, too.

Storm clouds at sunset over the ocean. Seychelles

Carbon cycle

The carbon cycle is the natural process by which carbon gases are emitted and absorbed across the globe. This determines the overall levels of carbon gases in the atmosphere.

Polar bear (Ursus maritimus) on edge of an ice floe.

Tipping points and feedback effects

As the Earth warms, the impacts can fuel each other and cause runaway, irreversible changes.

For instance, polar ice reflects sunlight away from the Earth. But when it melts (and predictions suggest Arctic sea ice will be mostly gone in summer within the next few decades), more heat will be absorbed instead. Also, thawing permafrost releases trapped methane, and drying forests and warming oceans emit their stores of carbon dioxide – all further increasing the greenhouse effect.

How you can help tackle climate change