Global warming? Climate change? What’s it all about?
We know some people find the whole issue of climate change confusing. A few still debate whether it’s really happening, and its causes. Others argue over the best ways of controlling it. Our easy-to-follow guide will bring you up to speed on the science and clear up misconceptions.
Carbon dioxide (CO2) – a natural gas, 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 are burnt as fuel). Other than water vapour, it’s the most common ‘greenhouse gas’.
Greenhouse gases (GHG) – including carbon gases like carbon dioxide and methane, are 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...
Carbon cycle – the natural processes that emit and absorb carbon gases across the globe, determining the overall levels of carbon gases in the atmosphere.
Human activity – over the past 150 years, the world’s industrialised nations have unwittingly changed the balance of the carbon cycle by burning huge amounts of fossil fuels (concentrated carbon, like coal, oil, gas), as well as breeding vast numbers of methane-producing livestock, and cutting down the forests that naturally absorb carbon dioxide from the air.
The extra carbon in the atmosphere has been raising global temperatures, and the speed of change has been faster than any natural process, and faster than most natural systems can adapt.
Global warming – doesn’t mean we’ll all have warmer weather in future. As the planet heats, climate patterns change, with more extreme and unpredicted weather across the world – many places will be hotter, some colder. Some wetter, others drier.
We know the planet has warmed by an average of nearly 1ºC in the past century. Might not sound much, but on a global scale that's a huge increase that's creating big problems for people and wildlife.
- 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 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).
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. When it melts (and Arctic sea ice is already predicted to be mostly gone in summer in the next few decades), more heat will be absorbed. And thawing permafrost releases trapped methane, just as drying forests and warming oceans emit their stores of carbon dioxide, all further increasing the greenhouse effect.
Beyond 2º – scientists predict possible rises of up to 6º this century if we don’t drastically cut greenhouse gas emissions.
We barely want to think 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.
A global climate deal – this is still urgently needed to set strict and binding greenhouse gas emissions targets on the developed, industrial nations – as the ones who largely caused the problem while benefitting from the commercial gains.
We need to cut GHG emissions at least 40% (below 1990 levels) by 2020, and at least 80% by 2050.
A fair global deal must also put money aside to assist developing countries to adapt to the unavoidable impacts of climate change, and to compensate them for unavoidable loss or damage, and to help them grow as low-carbon economies.
Cap and trade, and other forms of carbon emissions trading – where a limit is put on total emissions and industries and countries buy and sell their entitlements – may be useful. But it's certainly not a magic bullet, and could be open to abuse, so must be carefully controlled.
Climate change denial – some people might try to tell you: "Global warming is natural" or "The Earth is actually cooling" or "There's nothing we can do anyway"...
Here's wha the science is telling us:
- the Earth’s climate has always changed, and 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.
- the overwhelming evidence is that the global warming we're seeing now is mostly man-made, through our burning of fossil fuels and large-scale land use change like deforestation. It's not part of any natural process, no matter how much climate change deniers may wish to believe otherwise