Human influence on climate is clear, and urgent action is needed

The United Nations Intergovernmental Panel on Climate Change (IPCC) published in late September the first of three volumes of the fifth Assessment Report (AR5). Climate changes over past few hundreds of years have been unprecedented, says the Working Group One report, entitled Climate change 2013: the physical science basis, which states that ‘it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.’

The report states with at least 66% certainty that the last three decades have been the warmest in 1,400 years. Global temperatures have risen by 0.9°C in the last century, and the study lays bare the role of the oceans in storing a lot of this heat, an effect that could detrimentally affect marine life and which will result in rising sea levels due to thermal expansion.

If emissions continue as they are, by 2050 there is likely to be a further temperature rise of between 1.4°C and 2.6°C, claims the report. This could be reduced to between 0.4°C and 1.6°C, but only if emissions were halted almost immediately and carbon dioxide (CO₂) was then actually extracted from the atmosphere. ‘Substantial and sustained’ cuts in carbon emissions need to be taken to limit the effect of heat waves, melting ice and sea level rise, and extreme weather, it adds. The report also highlights the dramatic loss of ice from ice sheets and sea ice, particularly in the northern hemisphere.

Some that doubt the science behind climate change had pointed to a disparity between carbon levels in the atmosphere and the level of warming seen over the last 15 years. The report explains this as natural variability in the climate system due to other factors affecting temperatures, such as solar activity, and repeats that the long-term climate trend is consistent.

Responding to sceptics of climate science, the EU’s Climate Action Commissioner Connie Hedegaard said: ‘The issue is not whether to believe in climate change or not. The issue is whether to follow science or not. The day when all scientists with 100% certainty warn you against climate change, it will be too late. If your doctor was 95% sure you had a serious disease, you would immediately start looking for the cure. Why should we take bigger risks when it’s the health of our planet at stake?’

AR5 is different to previous IPCC reports, in that it recommends a ‘carbon budget’ to stay below the well-quoted 2°C limit to avoid ‘dangerous’ climate change. In this section it states that around half of the maximum level of CO₂ that can be emitted to stay below this threshold has already entered the atmosphere.

There are still uncertainties, particularly around ‘climate sensitivity’ – how the atmosphere will respond to a given amount of carbon dioxide entering it. The best guess for this has been lowered in AR5, but only by a small amount.

Commenting on the report findings, UK Secretary of State for Energy and Climate Change Edward Davey said: ‘The risks and costs of doing nothing today are so great, only a deeply irresponsible government would be so negligent. Without urgent action to cut greenhouse gas emissions this warming will continue, with potentially dangerous impacts upon our societies and economy. This strengthens the case for international leaders to work for an ambitious, legally binding global agreement in 2015 to cut carbon emissions.’

He noted that the UK is committed to reducing its emissions by 34% by 2020 and 80% by 2050, compared to the 1990 baseline. These targets are enshrined in law – the Climate Change Act (2008) – and the government’s performance against them is monitored by an independent Climate Change Committee. The energy sector, transport and economy is progressively being decarbonised, and the proposed Energy Bill will enable low carbon technologies to compete in the electricity market and attract investment.

Internationally, the UK is working towards a binding global deal to reduce emissions at the United Nations Framework Convention on Climate Change (UNFCCC) Conference of the Parties in 2015. The UK government agreed, as part of the European Union (EU), to enter the second commitment period of the Kyoto Protocol and is pressing the EU to move to a 30% emissions reduction target by 2020 and 50% by 2030 in the context of a global comprehensive agreement on climate change. Alongside this, the UK is providing £3.87bn through its International Climate Fund (ICF) to support developing countries, to demonstrate low carbon development, protect forests and to help the poorest countries adapt to the impacts of climate change.

*The full IPCC report can be found at http://www.ipcc.ch/

News Item details

Region: Worldwide

Subjects: Policy and Governance, Sea-levels, Carbon emissions, Carbon dioxide