How has our climate changed?
Our climate is continually changing. Fossils are evidence for this change, they tell us at what certain times the world has been warmer than it is now and about the little ice age on the North Pole. There is also evidence to suggest that at other times the ice cover was much greater than it is today.
This Evidence is collected by:
- Ice Cores- locked inside ice are molecules and trapped air. These are preserved year on year with more snowfall. Subtle changes in temp. cam be measured from ice cores extracted from Antarctica
- Weather Recordings - thermomerers are more accurate now and digital readings can be recorded remotley
- Rocks and Fossils - these can be studied for information covering longer time periods, for example, limestone found in Yorkshire would have been formed on the bottom of a warm seabed millions of years ago
- Analysis of pollen and trees
- Ice cover - Areas such as Greenland and the Arctic have seen thinning of ice sheets
- Glacial Retreat - photos show that many mountain glaciers have retreated in the last 50 years. However this could partly be due to a lack of snowfall.
Since about 1950 there is evidence of a steep climb in global temperature compared to the past. This trend is called global warming
For the last 10,000 years our climate has averaged about 14oC globally. However in the last 100 years, our climate has started to change rapidly. This is believed to be due to human causes.
- Increase in temp. have been recorded on land and in the oceans
- changes to the rainfall pattern have been observed - these are sometimes more extreme, meaning thst they are either alot wetter or alot dryer than they were. At other times the rainfall pattern is out of season. The extreme rainfall in the UK during summer 2007 is an example. However, in general, UK summers are getting drier and winters are getting wetter
- The lengths of seasons are changing - the UK growing season is lengthening
Why has our climate changed?
There are natural changed in our climate. These are caused by:
- Variations in the energy from the sun
- The way the earth orbits the sun
- The way oceans transfer heat from one area to another
- Volcanic activity (dust particles released in an eruption can disrupt the atmosphere
Humans also cause change to our climate. Carbon Dioxide is released into the atmposphere from cars and burning fossil fuels. Other gases such as methane (produced from cow poo, decaying landfill and peat bogs) also contribute to this change.
Effects of climate change - Agriculture
- Crop yields are expected to decrease for all major world crops
- Agricultural land on the edge of deserts becomes unusable, through the process of desertification
- Crops could be wiped out in low-lying areas that suffer from flooding. With less crops available on the world marker, prices are likely to increase
- The growing season in some small areas will increase. his is a benefit to some places such as the UK as more crops could be grown.
Effects of climate change - Sea level changes
- coastal land is at risk, especially land on deltas, a landform formed at the mouth of a river.
- sea defences are under more stress
- low-lying land is threatened so the lives of 80 million people across the globe are threatened.
Effects of climate change - Water and Ice
- More mass movement can occur as glaciers melt
- Communities that use the melt water from glaciers may see this supply decrease. This is especially the case in Asia
- Economies that rely on skiing as a form of income may suffer as the skiing season is reduced or disapperas through lack of snow
- Locations suffering from water stress (demand being higher than supply) will increase in number
- Less fresh water will be available in coastal areas as it will mix with sea water, which is salty
Effects of climate change - Population
- People will migrate from areas suffering drought. Any that remain will be in danger of dying from starvation and lack of water
- 17 million people in Bangladesh alone will be threatened by flooding
- As the world population increases, more people will be living in cities located on the coast. More people will be affected by coastal flooding as a result.
Greenhouse Effect & consequences
The emission of greenhouse gases- such as carbon dioxide and methane as by-products of industry and agriculture is having a global impact on temperature and weather systems.
Consequences of resource exploitation
When fossil fuels are burned, they enter the atmosphere. CO2, in particular, is given off when fossil fuels such as oil and coal are burned. Although the gases have allways been present, their concentration is gradually increasing as more fossil fuels are burned.
The inequality in the use of resources between MEDCs and LEDCs is shown by measuring and comparing their carbon emissions per capita. Countries that use a lot of fossil fuels to produce energy to power industry, produce electricity and heat homes, also produce a lot of carbon gasses.
Scientists believe that the build up of so called greenhouse gases in the atmosphere acts like a blanket or greenhouse around the planet; heat is trapped inside the Earth's atmosphere. This is the greenhouse effect, and the resulting increase in global temperatures is called global warming.
- plants and trees need C02 and use it up. However, if there is too much CO2 in the atmosphere- due to factories and power stations, combined with a reduction in the number of trees, through deforestation - Co2 builds up in the atmosphere
- This build up of CO2 is believed to contribute to global warming thorugh the greenhouse effect. This is why CO2 is called a greenhouse gas
- The biggest producers of CO2 in the world are the United States (USA), China, Russia, Japan, India, Germany, UK, Canada, Italy and Mexico
- The largest producers by far are the USA and China
How the greenhouse effect works
It is thought that the build-up of greenhouse gases impacts on global temperature in two ways:
- The gases allow more of the sun's rays to enter the atmosphere. Some solar radiation is still reflected back into space by the outer parts of the atmosphere, but it's believed the amount reflected back is gradually reducing
- At the same time, the greenhouse gases absorb more of the solar radiation that is reflected back from the Earth's surface - trapping heat and keeping it in the atmosphere. The ability of the atmosphere to capture the Sun's warmth is essential for life on earth. But if significantly more warmth is being captured, this is bad news for the planet.
Another group of greenhouse gases includes the CFCs. CFCs have been responsible for depleting the ozone layer as they attack and destroy ozone molecules
- The ozone layer is a high level layer of gas in the stratosphere. The ozone helps to keep out harmful UV rays that cause sunburn to human skin and damage to plants
- The resulting ozone holes let this harmful UV radiation in and add to the greenhouse effect.
- CFCs can be used in aerosols, such as hairspray cans, fridges and in making foam plastics
- CFCs were banned in many countries in the mid 1990s after it was found that they were breaking up the Earths ozone.
- Scientists say the hole in the ozone layer over Antarctica could disappear within 50 years
Implications of global warming
Scientists, politicians and industrialists continue to debate the causes of global warming, with some arguing that is is a natural process that's been going on for centuries. However, the Intergovernmental Panel on Climate Change (IPCC)- established by the United Nationas in 1988 - has stated the evidence suggests that human activity does affect global warming, in particular through the release of greenhouse gases and the use of aerosols.
There is also a debate over how quickly the earth is warming up. Some scientists estimate that atmospheric temperatures could rise by 1.4oC - 5.8oC in the next 100 years. Others believe that they will rise more slowly
Global Carbon Emissions
- LEDs want to develop to catch up with the emissions of MEDs and this normally means using more energy and burning more fuel. so global warming could threaten development
- Global Warming could melt the world's ice caps and glaciers, leading to an increase in sea levels. Some scientists estimate that over the next hundred years sea levels could rise betweem 10cm and 90cm - making many coastal areas around the world uninhabitable
- Global Warming could also affect the weather patterns, leading to more droughts, flooding and extreme weather, such as hurricanes
- In the UK we are largely unaffected by the dangerous weather of the tropics, such as hurricanes or severe droughts. But some climatoligists argue that the UK climate is changing as a result of global warming, with the possibility of more frequent floods, water shortages and extreme weather conditions