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The UN’s Inter-Governmental Panel on Climate Change (IPCC) published the first volume of its 5th Assessment Report on The Physical Science Basis of Climate Change in Stockholm on 27 September. The report was finalised after a four day meeting attended by delegates from 110 countries and involving a number of the Report’s leading scientific authors. The UK was represented by officials from DECC and 11 leading authors from the UK.
Climate change is happening now and greenhouse gas emissions from human activities are the dominant cause. Climate change will continue over the decades and centuries to come in the absence of significant emission reductions.
This is the most significant report from the IPCC since its 4th Assessment Report in 2007 and its assessment of the state of the climate is the most comprehensive ever written and provides a strengthened body of evidence of man-made climate change since its last major review almost six years ago. 259 experts from 39 countries reached their conclusions by reviewing thousands of published research papers. The findings are agreed by governments of the member countries.
1. Is climate change happening?
Yes, and it is already happening now. The evidence for climate change is overwhelming:
- Temperatures have risen by about 0.8°C over the last century.
- Each of the last three decades has been successively warmer than the previous decade and the last 30 years was likely the warmest period in 1400 years in the Northern Hemisphere.
- The frequency of heat-waves and intense rainfall events in many regions has increased.
- The oceans are absorbing carbon dioxide and are becoming more acidic.
- Global sea levels have risen by 20cm since the beginning of the last century and the rise is accelerating.
- Glaciers are receding around the world and permafrost is thawing.
- Seasonal snow cover in the Northern Hemisphere is declining.
- Arctic sea ice cover in the summer has reduced on average by about 40% since 1979 and is happening much faster than anticipated.
2. Are humans responsible?
Yes, this new IPCC report confirms with 95% confidence that humans are responsible:
- It is extremely likely that human activity is the dominant influence on climate change over the last 50 years and is responsible for more than half of the observed global temperature rise.
- Greenhouse gases are at level unprecedented in 800,000 years – carbon dioxide (CO2) concentration is now 40% higher than pre-industrial and this increase is primarily due to burning fossil fuels and deforestation.
- Further evidence shows that human influence can been detected in atmosphere and oceanic warming, changes in rainfall, the reduction in glaciers and Arctic ice, and some climate extremes.
3. What’s going to happen?
As greenhouse gas emissions continue, warming of the globe will continue.
- Without serious efforts to reduce greenhouse gas emissions, global temperatures are likely to rise by more than 2°C over the next century and could rise by as much as 5°C.
- The risk of some extreme events, particularly heat waves and heavy rainfall, are expected to increase further in coming decades.
- Global sea level is predicted to rise between 0.26 and 0.81 m by the end of this century and it will continue to rise for centuries to come.
4. Does the recent slowdown in warming change our confidence in these conclusions?
No, the IPCC report states how confident the scientists are about each of the report findings.
- Some have drawn attention to the slower rate of temperature rise so far in the 21st century. However 10–15 year periods are too short to draw conclusions about long term climate change.
- The climate system is complex and periods of slow-down and speed-up in global temperature trends have occurred before and are expected to occur again.
- Warming of the planet is dominated by the heat entering the oceans, accounting for over 90% of the total warming and there is evidence the oceans continued to warm during this period.
- Furthermore during this period there is plenty of other evidence for continuing climate change - sea level rise has accelerated, Arctic summer sea ice has broken new records for low extent, and many areas of the world have seen extreme heat and more intense rainfall.
5. Should we be concerned?
Yes. Climate impacts will increase considerably with climate change.
- Most aspects of climate change will persist for centuries even if greenhouse gas emissions are stopped soon.
- Much of that climate change will be irreversible.
- Risks of damage will increase for centuries, especially with sea level rise.
- Before the last Ice Age (120,000 years ago) when the world was up to 2°C warmer, sea levels were 5 to 10 metres higher, largely due to melted ice.
6. What should we do about it?
This latest evidence re-emphasises the need for governments, businesses and individuals to tackle climate change by reducing emissions. Climate models indicate that:
- Limiting the effects of climate change will require large and sustained reductions in greenhouse gas emissions globally.
- To have a good chance of limiting global temperature rise to 2°C or less, which is the internationally-agreed target, cumulative global emissions needs to be limited to 1000 billion tonnes of carbon since the pre-industrial period. We have already emitted half that amount and emissions are growing.
- This provides a strengthened case for international leaders to act now to reduce domestic carbon emissions and to secure an ambitious legally binding global agreement in 2015.
7. What can I do about it?
Everyone can play their part. Here are a few things that you can do:
- The Government’s Green Deal scheme helps you make energy-saving home improvements, like insulation, so that you need to use less energy to heat your home. This scheme lets you pay for some or all of the improvements over time on your electricity bill. Repayments will be no more than what a typical household should save in energy costs.
- Smart Meters will be rolled out to all homes and business by 2020 as part of a Government initiative. Domestic consumers will also receive an in-home display alongside their smart meter, showing how much gas and electricity is being used and what it is costing. Smart meters will help people to become more aware of the energy they are using, and take control of their energy bills.
- There is also a wealth of valuable information and handy tips on how to reduce your own energy consumption and lead a greener life on the Energy Saving Trust website.
8. Is this the IPCC’s main report?
No. This is the first of three major IPCC reports in the 5th Assessment Report Series. The IPCC will be publishing an assessment of the impacts of climate change and options for adaptation in March 2014 and a few weeks later it will publish an assessment of the options for reducing emissions through mitigation measures. All these reports will be wrapped into a synthesis report to be published in October 2014.