FAQ

1. What is climate change?

Climate refers to the average weather experienced in a region over a long period, typically 30 years. This includes temperature, wind and rainfall patterns. The climate of the Earth is not static, and has changed many times in the past in response to a variety of natural causes.

Recent observed changes in global climate are likely to be due to a combination of both natural and human causes. The Earth’s climate varies naturally as a result of interactions between the ocean and the atmosphere, changes in the Earth’s orbit, fluctuations in energy received from the sun and volcanic eruptions. The main human influence on global climate is emissions of greenhouse gases such as carbon dioxide (CO2) and methane. At present, about 8.7 billion tonnes of CO2 is emitted globally each year, mostly through burning coal, oil and gas for energy. Levels of CO2 in the atmosphere reached 387.35 parts per million in 2009, an increase of 70 PPM since 1961. (Source: NOAA).

  • For a complete list of monthly CO2 levels from 1958 to the present day, see CO2now.org website.

The United Nations define the term climate change as referring only to changes in climate which can be attributed to human activity.

The Earth is kept warm by the greenhouse effect. Certain gases in the atmosphere (so-called greenhouse gases) absorb energy that is radiated from the Earth’s surface, and so warm the atmosphere. The greenhouse effect is a natural phenomenon without which life on Earth as we know it would not be possible, as the Earth would be 30°C cooler. However, our modern lifestyles have resulted in us releasing large amounts of greenhouse gases into the atmosphere, enhancing the greenhouse effect and so pushing up temperatures globally.

2. How is the global climate changing?

Average surface air temperature is the most useful way to describe the state of the global climate. Data comes from millions of thermometer measurements taken around the world from as far back as 1860. These observations show that temperatures have risen.

Graph showing global mean temperature from 1860 to 2009 (IPCC)

Graph taken from IPCC AR4 FAQ 3.1.

Expressed as a global average, temperatures have increased by nearly 0.8°C since the late 19th century, and by about 0.2°C per decade over the past 25 years. The 16 warmest years on record have all occurred since 1990, with 1998 as the warmest and it is likely that the last 100 years were the warmest century in the last millennium. See the Warmest years page for further details.

The increase in global temperature has been accompanied by:

  • An increase in night-time temperatures over many land areas at about twice the rate of day-time temperatures.
  • An increase in the length of the freeze-free season in many Northern Hemisphere mid-to-high latitude land areas.
  • More intense rainfall events over many Northern Hemisphere mid-to-high latitude land areas.
  • A near worldwide decrease in mountain glacier extent and ice mass.
  • A decrease in Northern Hemisphere sea-ice amounts and a substantial thinning of Arctic sea-ice in late summer.

3. How is the UK’s climate changing?

One of the longest continuous temperature records in the world – the Central England Temperature (CET) series – shows that temperatures have increased by 0.7°C in the UK since 1659. Of that, a rise of around 0.5°C occurred in the 20th century. (Source: Hadley Centre).

The 1990s was the warmest decade in central England since records began, and 8 of the 10 warmest years since 1659 have occurred since 1990. The warming over land has been accompanied by warming of UK coastal waters.

Other climate indicators show a variety of changes for the UK climate:

  • The growing season for plants in central England has lengthened by about one month since 1900.
  • Heatwaves have become more frequent in summer, while there are now fewer frosts and winter cold spells.
  • Winters over the last 200 years have become much wetter relative to summers throughout the UK.
  • A larger proportion of winter precipitation (rain and snow) now falls on heavy rainfall days than was the case 50 years ago.
  • After adjusting for natural land movements, the average sea level around the UK is now about 10 cm higher than it was in 1900.

4. What evidence is there that the climate change is happening?

Most climate scientists agree that the world is going to get warmer. The Intergovernmental Panel on Climate Change (IPCC) was set up by the World Meteorological Organisation and the United Nations Environment Programme in 1988 to assess scientific and socio-economic information on climate change and its impacts, and to advise the United Nations Framework Convention on Climate Change.

In 2007, the Fourth Assessment Report from the IPCC reported that the likely range of global average warming by the end of this century is between 1.1 and 6.4°C, relative to 1980-1999.

The range of projections reflects a number of uncertainties, including those associated with the climate models and feedbacks, natural climate variability and future emissions of greenhouse gases.

5. Is the warming a consequence of human activities?

In 2007, the IPCC concluded that:

“Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations”.

Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns.

Recent temperature rises can only be explained by human activities, as illustrated in the graphic below. Computer models that simulate climate demonstrate that other variations, such as the sun’s output and changes in volcanoes (shown below as blue ‘plumes’) cannot account for all the observed warming (black line). Only when both human activities and natural variations are included in the models do they match the observed changes (pink plumes).

Maps showing continental warming across the globe

Image taken from IPCC AR4 WG1, FAQ 9.2.

Recent work by scientists at the Met Office examined the 2003 summer heatwave. Based on analysis of the observational record of summer temperatures in Europe, they estimate that it is very likely (>90%) that human influence at least doubled the risk of a heatwave of this magnitude occurring (Stott, P.A., Stone, D.A. and Allen, M.R. 2004. Nature 432, 610-614, 02 Dec 2004).

6. Can we prevent climate change by reducing emissions of greenhouse gases?

Experiments using global climate models show that when we reduce emissions of carbon dioxide, we reduce the rate of rise of average global temperatures and so lessen the rate and impacts of climate change. Changing our behaviour will slow the rate of warming.

However, once released into the atmosphere, carbon dioxide remains there for about 100 years. So even if we reduce emissions, we are committed to a certain amount of warming. In 2007, the IPCC concluded that if all greenhouse gas emissions were held at 2000 levels, a further global average warming of 0.3 to 0.9°C can be expected by the end of the century owing to greenhouse gases currently in the atmosphere.

7. What’s the difference between global warming and climate change?

Global warming refers to the increase in the average temperature of the Earth’s atmosphere. Climate change refers to the changes in climate that might accompany the warming of the atmosphere, such as changes in the frequency and intensity of extreme weather and sea level rise. Many people use these expressions interchangeably, however, the word warming may be misleading as it doesn’t embrace the full range of possible changes.

8. Isn’t there a chance that Northern Europe could get much colder?

The climate of the UK is affected by the Gulf Stream, which brings warm water from the Gulf of Mexico across the Atlantic Ocean to north west Europe. This warm water keeps the climate of the UK warmer than continental locations at similar latitudes. Some scenarios of climate change suggest that with further climate change, the North Atlantic Thermohaline Circulation (THC), of which the Gulf Stream is a part, could shut down. This would cause average temperatures in the UK to drop by some 4°C. Research at the Met Office shows that global warming could reduce the strength of the THC circulation by 25% by 2100. However, the direct heating from global warming would be greater than any cooling effect from reduced activity of the THC. A cold future is therefore very unlikely.

9. What are greenhouse gases?

Greenhouse gases are naturally occurring gases in the atmosphere that have the capacity to absorb long-wave radiation emanating from the Earth’s surface. By absorbing this energy and re-radiating it, the gases cause the temperature of the Earth’s lower atmosphere and surface to increase. The most common greenhouse gases are water vapour and carbon dioxide. Others include methane and nitrous oxide. Man’s activities have increased concentrations of all of these gases and have also introduced new ones, such as CFCs.

10. Why would sea levels rise if it gets warmer?

Oceans absorb heat from the atmosphere, so the ocean warms with the atmosphere. When water is warmed, it expands, causing sea levels to rise. In addition, as the temperature of the oceans and atmosphere increases, so permafrost, glaciers and ice sheets melt, releasing additional water into the oceans and contributing to sea level rise.

In addition, the UK and northern Europe are still responding to the melting of ice sheets that covered the land during the last Ice Age. Mainland Britain is slowly tilting, with South and East England slowly sinking into the sea and the North West and Scotland rising – this is known as Glacial isostatic adjustment (GIA). Sea level rises around the UK would increase the risk of flooding and coastal erosion.

11. Will climate change mean we experience more extreme events?

The type, frequency and intensity of extreme events such as heatwaves, droughts and floods are expected to change as the Earth’s climate changes.

In a warmer future climate, there will be an increased risk of more intense, more frequent and longer-lasting heatwaves, such as the European heatwave of 2003. Most global climate models project that a warming of future climate results in increased summer dryness and winter wetness for many places in northern middle and high latitudes (like the UK), indicating a higher risk of winter flooding and summer droughts.

It is also important to remember that individual extreme events cannot be taken as proof that the climate is changing.

12. Where can we get more information about the science behind climate change?

For useful sources of information about climate change, please see the Connections section.

The definitive source of information about climate science is the Intergovernmental Panel on Climate Change (IPCC). The IPCC was established in 1988 by the World Meteorological Organisation (WMO) and the United Nations Environmental Program (UNEP). Its role is to assess on a comprehensive, objective, open and transparent basis the scientific, technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change, its potential impacts and options for adaptation and mitigation. The fourth and latest IPCC Assessment Report, AR4, was published in 2007.

The BBC has an extremely comprehensive section on climate change, including a simple Q & A page and an animated guide.

13. Why think about how climate change will affect us now when its effects won’t be felt for many years?

The earlier you find out the likely impacts, the more options you have for adapting, including taking advantage of opportunities. This is particularly important when it comes to major investment decisions and decisions that may affect whole sectors, or communities. In addition, the sooner we take action to reduce emissions, the greater the chance of stabilising the climate.

14. Isn’t the UK a winner in terms of climate change? If so, why worry so much?

The UK will be warmer and this will certainly bring some potential opportunities. However, we are also likely to experience more extreme weather and we need to start planning now to deal with the consequences, such as additional flooding, drought and sea level rise. There are also likely to be serious implications for other parts of the world, and effects on, for example on the global trade network, that will have also an impact on the UK.

15. Why doesn’t UKCIP concentrate on preventing climate change?

Some climate change is inevitable because of the greenhouse gases that human activity has already generated, so UKCIP was set up by the UK Government to co-ordinate research into the impacts of climate change and to help organisations assess how they will be affected so they can plan to adapt. There are other agencies whose purpose is to help reduce greenhouse gas emissions and so limit the impact of climate change (known as climate change mitigation). UKCIP’s work on climate change adaptation is complementary to the work going on to limit climate change.

16. Where can my organisation find funding for research?

UKCIP does not fund research itself. To date, most research into the impacts of climate change has been undertaken in partnership between organisations, with each organisation contributing according to their budget. You can contact us for advice if you are interested in undertaking research into climate change impacts and adaptation.

17. How much climate change can we expect over the next few years?

The UK Climate Projections (UKCP09) do not provide any information on changes expected in the short term (i.e. next few years) as they express averages over 30-year time periods. Short term projections of climate are difficult due to the dominance of natural climatic variability (such as that produced by El Niño Southern Oscillation) on annual or decadal time-scales.

18. Where can I find out more about flooding?

The UK Climate Projections (UKCP09) do not say anything about how the projected changes might affect the frequency of or areas at risk from flooding.

The three agencies who can advise you as to whether your property is in the floodplain and offer information on how to protect yourself, your family and your property against flooding vary according to your location:

19. Where can I find out about international negotiations to reduce emissions?

International negotiations, including the Kyoto Protocol, were established and are overseen by the United Nations. The UNFCCC hold an annual Conference of the Parties, usually in late autumn.

20. Do the UK Climate Projections (UKCP09) include the possible shut-down of the Gulf Stream?

Yes. The Gulf Stream (properly termed the Meridional Overturning Circulation, or MOC) in the North Atlantic is represented in all the full coupled atmosphere-ocean global climate models used in UKCP09.

Research into the thermohaline circulation is ongoing by many research centres including the Hadley Centre and NERC (through the RAPID research programme).

21. How reliable are climate models?

Climate models are a mathematical description of our understanding of the processes in the Earth’s climate system; atmosphere, ocean, land, cryosphere. Their reliability is measured by:

  • Comparing their representation of the current climate and observations, including means as well as variability and extremes.
  • Driving them with the best estimates of changes to climate forcing mechanisms over the last 150 years (natural, such as volcanoes and solar radiation, and man-made such as greenhouse gases and aerosols) and comparing the model simulations with observations of trends over the same period.
  • Validation by comparing model simulations of climates many thousands of years ago with reconstructions of climate of the period (so called palaeoclimatologies). Validation exercises provide compelling evidence that, in terms of gross temperature response, the model is effectively reproducing what has been observed.

More detail on model validation and performance can be found in Chapter 8 (Model Evaluation) of IPCC AR4.

22. Weather forecasts aren’t accurate for more than a few days ahead, so how can we possibly predict climate over the next 100 years?

A weather forecast tells us what the weather (for example, temperature or rainfall) is going to be at a certain place and time over the next few days.

A climate change projection tells us about changes in the average climate, its variability and extremes. It will not make a specific forecast for a definite date in the future.