60 second guide to… Climate change

The changes in the Earth's climate over the past century are unusually rapid, so what’s causing them? Most experts agree that humans have had a big impact

What is climate change?

The term “climate change” refers to these changes in the world’s atmosphere. It includes a rise in average global temperature and changes in rainfall, and other weather patterns.

It's getting warm in here

Scientists have shown that the Earth’s average surface temperature is around 0.8ºC warmer than it was a century ago. Along with 1998, the first five years of the 21st century were the hottest ever recorded.

The Intergovernmental Panel on Climate Change predicts a rise of between 1.1 and 6.4 ºC in the next century.

Humans and climate change

The temperature of the Earth is partly determined by the greenhouse effect. This is the phenomenon by which heat from the Sun is trapped in the atmosphere by certain gases, including the water vapour in clouds. If the greenhouse effect didn’t exist, the average temperature on Earth would be around -18ºC.

Humans boost the naturally occurring greenhouse effect by releasing extra greenhouse gases, the most important of which are carbon dioxide (CO2) and methane (CH4).

What will change?

Climate change is producing other changes besides higher temperatures. For example, sea levels are rising due to ice sheets melting and warmer water has a natural tendency to expand slightly.

Rainfall patterns have been affected too. Some areas have recorded a rise in rainfall, some are seeing less and other areas are experiencing the same amount falling in intense bursts.

The intensity of hurricanes is also increasing and so is the threat posed by the possibility of flooding caused by storm surges.

The effect on humanity

The impacts will range from an increase in floods and droughts through to the displacement of people in low-lying areas because of rising sea levels. Disease patterns could also change as insects and parasites move to new areas.

Many of these impacts are already being observed. One study by the World Health Organisation suggested that, in 2000 alone, more than 150,000 people died as a result of climate change.

Too hot to handle

If the climate gets too hot, the warming could become self-reinforcing and impossible for us to stop. To have a fair chance of avoiding that, we need to limit future temperature rises to around 2ºC.

Around a quarter of that rise is already inevitable, due to the gases we’ve already released and global emissions are still rising fast. We may have a window of just a decade or so to reduce emissions and avoid runaway climate change.

What is the Kyoto Protocol?

The Kyoto Protocol is a treaty under which many developed nations agreed to cut their greenhouse gas emissions. The targets varied between countries, though the average was a 5.2 per cent reduction (relative to 1990) by 2012. The US and Australia both signed up to Kyoto but decided not to ratify it.

Kyoto will not make a huge cut in global emissions, which are rising all the time, but discussions are underway about the follow-up agreement for after 2012.

The Bali 'roadmap'

In December 2007, delegates from all over the world gathered in Bali, Indonesia, to discuss the post-2012 follow-up to Kyoto. All the participating nations, including the US, acknowledged the need for "deep cuts in global emissions". Despite this, no specific targets were agreed.

Instead, the result was a "roadmap" for negotiations running up to the 2009 climate summit in Copenhagen, Denmark. Views are mixed on whether the Bali conference was a success or a failure.

The facts about China's emissions

China’s emissions are rising fast but the nation has already taken some steps to minimise them, such as increasing fuel efficiency standards for cars.

The emissions per person in China are still much lower than those in the West. And many of the country’s emissions are caused by producing goods for Europe and the US.

A possible solution

Although some climatic shifts are unavoidable, runaway climate change is not yet inevitable. But to secure a good chance of preventing it, we need to slash greenhouse gas emissions within the space of just a few decades. Considering that emissions are rising steeply, this presents a huge diplomatic, technological and cultural challenge.