World warned: Act now or humanity faces catastrophe

Alok Jha

Former Science Correspondent

A graveyard in Somerset was left partially submerged by severe flooding during heavy storms earlier this year. Credit: Reuters/Toby Melville

Even at the level of the UK, the impacts of climate change get clearer every year. The period from January to September this year was the warmest such period for the UK since records began in 1910, and seven of the 10 warmest years in the past century have occurred since 2002. Storms lashed the country earlier this year, heatwaves are on the rise and spring arrives earlier every year.

Today, the Intergovernmental Panel on Climate Change (IPCC) issued its verdict on the changes to the global climate. The human effect on climate was unequivocal, it said, and climate change is already having impacts around the world on everything from human health to biodiversity and weather. In future, the world faced a "very high risk of severe, widespread and irreversible" impacts without immediate action to cut greenhouse gas emissions.

The world has a small window of opportunity, the IPCC said, to prevent temperature rises, after which the costs of action would be greatly increased.

This was the fifth assessment report from the IPCC - a collaboration of thousands of scientists and hundreds of government representatives - which spent years looking at the state of the evidence for climate change. They looked at more than 30,000 scientific papers on the state of our world over the past year and have published several reports on the causes of climate change, its impacts and potential solutions in the past 12 months. Today they published a synthesis of all of that work and laid out a final assessment for policymakers.

To prevent dangerous climate change, scientists and political leaders have generally said that we need to prevent the global average temperature from rising by no more than 2C by the end of the century. In the IPCC’s synthesis report, the authors said that this would require substantial cuts to greenhouse gas emissions from, for example, power stations - between 2040 and 2070, the energy sector will need to reduce its emissions by 90% or more below 2010 levels. The share of low-carbon electricity will have to rise from the current share of 30% to more than 80% by 2050 and that fossil fuel power generation that doesn’t have technology to capture and store waste CO2 at the source (rather than dumping it into the atmosphere) should be “phased out almost entirely by 2100”.

If we can’t cut emissions, warns the IPCC, the world risks warming of 5C or more by the end of the century. The effects of this temperature rise - increased storms, droughts, rising sea levels and melting of ice at the polar ice caps - will be catastrophic for humans as well as plants and animals.

Today’s report is the last major chance that scientists have to set out the most robust evidence for climate change and make the implications of each subsequent course of action as clear as they can for countries. The next step is for policymakers in governments around the world to argue about what to do about the change that the scientists have predicted.

Lord Nicholas Stern of the Grantham Research Institute on Climate Change and the Environment at London School of Economics, said the IPCC’s “comprehensive report about the causes and potential consequences of climate change should be essential reading for all political leaders across the world". He added:

Australian Prime Minister Tony Abbott's reluctance to act on climate change warnings has been met by protests across the country. Credit: Reuters/David Gray

All of the discussion by international governments in the next 12 months will culminate in a two-week meeting in Paris in December 2015, when they will come together to (hopefully) agree a treaty to curb emissions and set the world on a path to preventing the worst effects of climate change.

“We have the means to limit climate change,” said Rajendra Pachauri, chairman of the IPCC, adding:

Lord Stern added that today’s report posed a challenge for the Australian Prime Minister, Tony Abbott, who has so far refused to allow climate change to be a major agenda item for the G20 summit in Brisbane later this month.

Mr Pachauri said that the scientific case for prioritising action on climate change was clearer than ever.