	Environmental Policy & Sustainability
	Torbay Council
	Roebuck House Abbey Road Torquay TQ2 5TF
	sustainability @torbay.gov.uk
	01803 207751
	01803 208882

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Climate Change FAQs

What is the greenhouse effect?

The greenhouse effect is a natural process that warms Earth’s lower atmosphere by 33°C to create a comfortable average global temperature of 15°C.

The process starts when short wave radiation, emitted from the sun, penetrates the Earth’s atmosphere and arrives at its surface. Approximately half of this radiation is immediately reflected and returned to space, while the other half is absorbed, causing the temperature of the land and oceans to increase. This in turn leads to the emission of heat in the form of long wave infra-red radiation up towards the atmosphere. Infra red radiation is less capable of passing through the Earth’s atmosphere and can become trapped by greenhouse gases. The trapped heat causes a warming of the lower atmosphere (see below).

Water vapour, Carbon Dioxide, Methane, Nitrous Oxide and Ozone are the main naturally occurring GHGs. These are accompanied by synthetic chemicals, foremost Chlorofluorocarbons, Hydrofluorocarbons, Perfluorocarbons and Sulphurhexafluoride that until recently were extensively used as aerosol can propellants and refrigerants in air conditioning units and freezers.

Is the Earth's climate really hotting up?

During the past 100 years, global average surface temperature increased by about 0.7°C. Ice core, tree ring and other measurements tell us that average Northern Hemisphere temperatures during the second half of the 20th century were likely to have been the highest in at least the past 1300 years. Eleven of the past 12 years were the warmest we have experienced since 1860.

In addition to warming of the Earth's surface, there has been an increase in heatwaves, warming of deep oceans, fewer frosts, retreat of glaciers and sea ice and a rise in sea level during the 20th century of approximately 17 cm. Many species of plants and animals have changed their location or the timing of seasonal activities in ways that provide further evidence of climate change.

Hasn't the Earth's climate always changed?

Throughout history, the Earth has experienced cold and warm periods, including ice ages and interglacial periods (warm periods). Over the past million years, these natural climate changes were due to variations in Earth's orbit that affect the amount of sunlight reaching its surface. Ice ages historically have extended over about 90,000 years and the warmer interglacials have lasted about 10,000 years. Greenhouse gas concentrations changed with the temperature variations and caused about half of the magnitude of the climate changes.

Complex natural fluctuations still affect the Earth's surface temperature and climate over long timescales. However, simulations using sophisticated computer-based climate models confirm that climate change during the past 50 years was mainly caused by human activities that have increased atmospheric concentrations of greenhouse gases, while the variations in the Sun's output, aerosols and land use have had smaller impacts.

The current global concentrations of carbon dioxide in the atmosphere (approaching 380 parts per million) are the highest in the last 650,000 years. The rate of increase in carbon dioxide during the industrial era is very likely to have been unprecedented in more than 10,000 years.

Climate models indicate that, over the next century, a climate change of 1.1-6.4 °C will occur. This rate and magnitude of warming are significant in the context of the past 400,000 years.

How do we know that recent climate change is attributable to human activities rather than natural causes?

The present atmospheric concentration of carbon dioxide has not been exceeded for the past 650,000 years, and possibly not for 20 million years. Ice core records show that carbon dioxide levels in the atmosphere varied between 180 and 280 parts per million (ppm) due to glacial cycles. For the past 10,000 years global atmospheric carbon dioxide has been quite stable at between 260 and 280 ppm, and level at about 280 ppm from 1000 to 250 years ago.

However, since the beginning of the Industrial Revolution, some 250 years ago, the concentrations of greenhouse gases in the atmosphere have increased dramatically. Human activities, such as burning fossil fuels (coal, oil and gas), deforestation and agricultural practices have increased carbon dioxide concentrations by more than a third (to approximately 380 ppm). The rate of increase in carbon dioxide during the industrial era is very likely to have been unprecedented in more than 10,000 years.

The observed changes in climate, especially temperature increases since about 1970, cannot be explained solely by natural causes such as solar activity. Reconstructions of climate data for the past 1000 years indicate that this recent warming is unusual and is unlikely to have resulted from natural causes alone.

When only natural factors, such as volcanic aerosols and solar activity, are included in computer model simulations of the climate in the 20^th century, the simulations do not explain the observed warming in the second half of the century. The warming in the second half of the century can only be explained if human-induced changes in greenhouse gases are included in the models.

What is the carbon cycle? How does human activity contribute to the carbon cycle?

Carbon, in various forms, continuously circulates between the living world, the atmosphere, oceans and the Earth's crust. There are many different processes by which carbon is exchanged between these locations. Events, such as fires, which release carbon dioxide into the atmosphere, are known as ‘sources'. The oceans and growing trees remove carbon dioxide from the atmosphere and are known as ‘sinks'.

Plants grow by absorbing carbon dioxide from the air or water and converting it to plant tissue through photosynthesis. Some of this carbon is used to supply the plant with energy. This process, known as respiration, releases carbon dioxide back into the atmosphere. The carbon from carbon dioxide absorbed by a tree may be stored as wood for hundreds of years. Or the carbon may become part of a leaf that dies and decomposes, with the carbon returning to the atmosphere relatively quickly.

The surfaces of the oceans also release and absorb carbon. This absorption occurs when carbon dioxide in the air dissolves in the top layer of sea water and through photosynthesis by marine plants.

Each year human activity adds several billions of tonnes of carbon in the form of carbon dioxide to the atmosphere. A little over half of this carbon dioxide remains there, while the rest is absorbed by plants and the oceans.

It only takes a small change in the amount of carbon entering the atmosphere to upset the balance. The burning of fossil fuels by humans adds about 6.5 billion tonnes of carbon each year in the form of carbon dioxide.

Proof that more carbon dioxide is being added to the atmosphere than removed is the fact that concentrations of the gas continue to rise. Furthermore, scientific techniques reveal that this additional carbon dioxide originates from fossil fuel combustion.

Will a few degrees warming have a significant impact on our climate?

The world has warmed 0.7°C in the past century. Scientists are confident that the world will get warmer in the 21st century due to further increases in greenhouse gas concentrations, with globally averaged surface temperatures likely to increase by 1.1-6.4 °C from 1990 to 2100. Warming of a few degrees may seem minor compared with day-to-day or seasonal variations in temperature. However, in global climate terms it is much larger than any of the climatic changes experienced during the past 10,000 years.

During the last ice age, which was at its maximum about 70,000 years ago, surface temperatures were on average about 5°C lower than today, and much colder in the polar regions. Sheets of ice covered almost one-third of the world's land. The climate change projected in the 21st century would occur at a time that is already one of the warmest for hundreds of thousands of years, with current levels of carbon dioxide not exceeded for the past 650,000 years, and not likely exceeded during the past 20 million years.

A few degrees of climate change will lead to more heat waves and fewer frosts.

More fires and droughts are expected in some regions of the world and more intense rainfall and resultant flooding in other areas. The Intergovernmental Panel on Climate Change Fourth Assessment Report says that sea level is likely to rise by 18 to 59cm by 2100, but this does not include possible changes in big ice sheets such as Greenland and the Antarctic that could lead to more rapid sea level rise. Low-lying coastal areas and islands will be inundated more often by storm surges.

How do scientists measure global surface temperatures?

Thermometers have recorded air temperature at weather stations or surface seawater temperature from ships for many decades, with almost global coverage extending back to 1861. Instruments on satellites have monitored infrared radiation for many years, which is then converted to temperature to provide global records back to 1979. In addition, proxy records—data relating to climate, such as tree rings and ice cores— extend the global surface temperature record back hundreds and even thousands of years.

How reliable are climate models?

Computer-based climate models use mathematical formulae to represent the important physical and chemical processes that drive the world's climate. They are the best tools available for making climate change projections. While the models still have shortcomings, there has been enormous progress over past years in our understanding of important climate processes and their representation in climate models.

Simulations that include estimates of natural and human influences can reproduce the observed large-scale changes in surface temperature over the 20th century, including the climate change that has occurred during the past 50 years.

Climate models are good at simulating most climatic variables that are needed for studying global and continental climate change. Climate models are also useful tools for exploring likely regional changes to climate.

How do scientists project future climate?

Our climate is the result of the interaction of the Sun's radiation with the atmosphere, oceans, polar ice and the land. Many processes contribute to our climate, including the absorption and emission of heat by materials such as gases and water, reflection of heat from different surfaces such as snow and trees and the circulation of the oceans and atmosphere.

Climate models are the best tools we have for projecting future climate. A climate model is a simplified mathematical representation of the Earth's climate system. Climate models can reproduce present climatic features reasonably well, along with past climatic changes such as the last Ice Age and the climate change of the 20th century.

Economists and other experts have developed a number of scenarios or possibilities for how the world might develop over the next century based on a set of assumptions, such as how fast population might increase and how quickly renewable energy sources might replace fossil fuels. In 2000, a set of greenhouse gas and aerosol emission scenarios for the 21st century were developed for use in climate model simulations. Research groups around the world use these scenarios to project climate changes.

The challenge facing us now is to determine how much we need to reduce our carbon dioxide emissions to minimise the risk of dangerous climate change.

How much will sea levels rise as the climate changes?

Global average sea level rose by approximately 17 cm during the 20th century. It is very likely that increasing temperatures in the 20th century contributed to this sea level rise through thermal expansion of seawater and widespread loss of glaciers.

The IPCC Fourth Assessment Report says that sea level is likely to rise by an additional 18 to 59 cm by the year 2100, but this does not include possible changes in big ice sheets such as Greenland and the Antarctic that could lead to more rapid sea level rise. This rise may affect low-lying islands and coastal settlements throughout the world.

As the Earth's surface warms, the oceans slowly absorb heat and expand, causing the sea level to rise. This thermal expansion of the ocean will be a major contributor to sea level rise during future centuries.

What amount of climate change is likely this century and can it be avoided?

Scientists are certain that climate change is already happening. Global average surface temperature increased over the past 100 years by about 0.7°C. It is very likely that the warming will exceed 1°C over the next century.

Once carbon dioxide is released into the atmosphere, it stays there for between 50 and 200 years. Hence further warming is already in the pipeline, regardless of what we do in the future. This is also because the deep ocean and the polar ice caps have massive thermal inertia, so they warm and cool more slowly than the atmosphere.

The level of action required to address the problem depends on the degree of climate change we are prepared to accept. A number of scientific assessments and governments have adopted a threshold for “dangerous” climate change of 2°C above pre-industrial levels. After accounting for the 0.7°C of warming that has already occurred, this allows less than 1.5°C of additional warming before the threshold is exceeded. Avoiding this level of warming by the year 2100 will require substantial global emissions reductions within the next 20-40 years.

What contribution do changes in the Sun's energy make to climate change?

The Sun's energy drives the Earth's climate. The amount of energy received by the Earth varies due to changes in the Sun's activity and changes in the Earth's orbit around the Sun.

During the 20th century, the climatic influence of natural factors probably increased (a warming effect) up to about 1950 due to a period of low volcanism and a small rise in solar radiation.

Since the 1970s, global temperatures have risen significantly. Measured solar activity over the last few decades has not significantly changed and cannot explain the continued warming trend. Rising concentrations of greenhouse gases are responsible for the bulk of the warming experienced in recent decades.

What are the potential impacts of climate change?

Projections for the 21st century suggest:

More heatwaves could result in heat stress and heat-related deaths in humans and livestock, and damage to crops.
Fewer cold and frosty days will reduce cold stress and cold-related deaths in humans and livestock, and reduce frost damage, but may extend the range of pests and diseases.
More intense and sporadic rainfall will increase flooding and associated loss of life, property and economic productivity. It would also affect soil erosion and pollution of rivers and oceans.
More frequent or intense droughts will increase loss of crops, livestock, fisheries and wildlife, and decrease river flows and water quality.
Changes in rainfall patterns and reduced soil moisture could reduce water supplies for agriculture, domestic and industrial uses, energy generation and biodiversity.

What are the changes expected for Torbay?

In 2002 the UK Climate Impacts Programme provided climate change prediction data at a 50km grid resolution, which have been used to identify the expected changes in Torbay’s climate.

In Torbay the average annual temperature will be up to 4°C higher by 2080 than it was in 1990. This would lead to a 50% reduction in summer rainfall and a 20% increase in winter rainfall as well as an increase in sea level of up to 90 centimetres. Changes to our climate on this scale will have wide ranging impacts upon agricultural practices, water resources, coastal defences, transport, public health, wildlife, landscape, and the composition and productivity of Torbay’s economy.

If we take immediate effective action to reduce our greenhouse gas emissions, the impending impacts of climate change upon society and the natural environment can be reduced.

What contributions do volcanic eruptions make to climate change?

Large volcanic eruptions can blast huge amounts of sulphur dioxide into the upper atmosphere (the stratosphere). There, the sulphur dioxide transforms into tiny particles of sulphate aerosol. These particles reflect energy from the Sun back into space, preventing some of the Sun's rays from heating the Earth.

Conversion of sulphur dioxide to sulphuric acid aerosol in the stratosphere takes some months, so maximum cooling occurs up to a year after the eruption. It may take many years before the cooling influence of the volcanic aerosol disappears completely.

When Mt Pinatubo in the Philippines erupted in 1991 it blasted up to 26 million tonnes of sulphur dioxide into the stratosphere. This led to a global surface cooling of 0.5°C one year after the eruption. This cooling offset the warming effects of both El Niño and human-induced greenhouse gases from 1991 to 1993.

What is the El Niño-Southern Oscillation (ENSO)?

The El Niño-Southern Oscillation (ENSO) is a variation in normal sea surface temperatures in the equatorial Pacific Ocean. Pacific Ocean trade winds propel surface water in a westerly direction along the equator. As a result warm water accumulates in the western equatorial Pacific, to the north-east of Australia, heating air in contact with it. The warm, moist air produces clouds and rain.

During the El Niño phase of ENSO the Pacific trade winds and tropical currents weaken, and the warm water in the western Pacific is displaced to the central Pacific. Clouds disappear and parts of Australia may experience drought. Simultaneously, parts of Northern and Southern America experience above-average rainfall.

In the opposite phase of ENSO, La Niña, the ocean surface in the equatorial eastern Pacific Ocean cools. Meanwhile, the western equatorial Pacific warm pool, north of New Guinea, warms. This in turn warms the air in contact with it which rises, lifting tonnes of moisture that condenses in the atmosphere forming massive cloud banks. These clouds bring rain to eastern Australia and parts of South-East Asia. La Niña's warmer seas usually generate more tropical cyclones around Australia.

Typically, El Niño and La Niña events occur every two to seven years.

What is the Intergovernmental Panel on Climate Change?

Recognising the problem of global climate change, in 1988 the World Meteorological Organisation and the United Nations Environment Programme established the Intergovernmental Panel on Climate Change (IPCC).

The role of the IPCC is to assess the scientific, technical and socio-economic information relevant to understanding the threat of human-induced climate change. The IPCC does not carry out new research nor does it make climate-related measurements. It bases its assessments mainly on published and peer-reviewed scientific literature.

The full report and summary for policymakers are available from the IPCC website at www.ipcc.ch.

Can cosmic rays affect Earth’s climate?

Any effect that cosmic rays could have on the climate is not yet very well understood but, if there is one, it is likely to be small. Cosmic rays are fast moving particles which come from space, and release electric charge in the atmosphere.

Experiments done in a laboratory hint that cosmic rays could play a role in the development of tiny particles that could in turn play a part in the formation of clouds. If this happens in the same way in the atmosphere - which isn't proven - it might lead to more clouds, which generally have a cooling effect by reflecting the Sun's rays back into space.

It has been proposed that this process would act to enhance the influences of the Sun on the climate. We know that when the Sun is more active its magnetic field is stronger and this deflects cosmic rays away from the Earth. So the argument is that a more active Sun would lead to fewer cosmic rays reaching the Earth, resulting in fewer clouds and therefore a warmer Earth.

However, observations of clouds and galactic cosmic rays show that the possible link between cosmic rays and clouds only produces a small effect. Even if cosmic rays were shown to have a more substantial impact, the level of solar activity has changed so little over the last few decades the process could not explain the recent rises in temperature that we have seen.