Past Climate Change
This graph shows how the Earth's temperature has cooled and warmed over the past 2000 years. It demonstrates long-term temperature changes due to natural causes.
Natural causes of climate change
- The Earth’s orbit changes a small amount once every 100,000 years. These are known as Milankovitch cycles
- The amount of energy radiated from the sun changes over a 11-year cycle
- Volcanic eruptions pump ash dust into the atmosphere causing a cooling effect
- Large asteroid collisions can cause cooling as the material blocks out the Sun.
- Asteroids hitting the Earth can cause huge fires which will release massive amounts of CO2 which will result in a warming effect.
- Ocean current changes can cause cooling and warming.
The Little Ice Age
- The Mini Ice Age was a colder period in northern Europe starting in the 15th century and lasting to the mid 19th century.
- It had various negative impacts on people;
- Crops did not grow well which meant people had to go hungry because there was less productivity and food.
- The winters were very cold and the summers were very short.
- It was most likely to be caused by natural changes, not humans because there was not enough people or industry to cause it. It could have been caused by:
- Fewer sunspots
- Volcanic ash in the atmosphere
- We can retrieve this kind of information from diaries, newspapers and paintings from the time. Also by looking at tree rings in old trees can tell us what the climate was like. The tree rings in old trees are thinner during cold years.
- During the Ice Age, Megafauna (big animals typically weighing over 40kg such as the woolly mammoth, giant beaver and sabre-toothed tiger) had evolved during the Ice Age.
- Once the Ice Age had ended, temperatures rose 5oC in 10,000 years
- The Megafauna couldn’t adapt to this change to a warmer climate and subsequently became extinct. Hunting by early humans could also be a factor in their extinction.
Present and future climate change
Most people agree that humans are causing climate change through the production of various greenhouse gases.
- The rise in greenhouse gases, such as Carbon Dioxide and Methane, matches the start of the Industrial Revolution.
- Current levels of Carbon Dioxide are thought to be at their highest for at least 650,000 years.
- Current levels of Methane are thought to be at their highest for at least 900,000 years.
- Methane is 21 times more potent than Carbon Dioxide.
As a country develops, more greenhouse gases are produced and released into the atmosphere.
More Carbon Dioxide is produced because...
- there is more industry
- more energy is needed so more fossil fuels are burned
- transport increases so more vehicles on the road consuming petrol/diesel
The Greenhouse effect
The UK climate
- The climate of the UK is mild and wet – temperate maritime.
- Several factors impact on the UK’s climate:
- Latitude affects how much Sun the UK gets and how strong it is during different seasons
- The North Atlantic current keeps the UK warmer than other places of the same latitude
- Air masses bring weather conditions with them. The UK is affected by five air masses
- The prevailing winds from the Atlantic Ocean in the south west. They pick up moisture from the sea and often bring rain to the UK.
- Possible changes to the UK’s climate include:
- Average temperature rise
- Less predictable rainfall patterns with drier summers
- Changing seasons – possibly longer summers and more extreme cold in winter
- Changes will happen because:
- The North Atlantic current is likely to move which will probably reduce sea temperatures and bring less rainfall
- More air masses will come from the north, bringing more storms and perhaps more extreme cold in winter
- The paths of depressions (which bring rain) may be altered by these changes in air masses and ocean currents
Impacts of climate change in the UK
- Sea level rise will lead to the loss of coastal land and increased erosion.
- More severe storms and longer summer droughts.
- Changes to fishing industries if fish species move to different waters.
- Ecosystem change could mean some plant and animal species move into new areas and new (invasive) species emerge.
- Warmer temperatures could encourage diseases such as malaria.
- Damage to cities such as London from flooding would be extremely disruptive and expensive
- Warmer weather may mean farmers can grow different crops and enjoy longer growing seasons
- Hotter summers could mean people spend more holidays here and not go overseas
- Cost of protecting places from flooding will be expensive and in some cases not practical.
Predicting the effects of climate change
If CO2 concentrations go over 550ppm, predictions are...
- global temperature rises will be 6oC or more
- millions of people would lose their home due to sea-level rises
- changes to world weather patterns would cause extreme weather such as droughts and storms leading to famines and disasters
- animal and plant species would not be able to adapt fast enough to the changes
If CO2 concentrations stay under 550ppm, predictions are...
- global temperature rises will not go above 2oC
- sea level might rise up to 1m, causing coastal flooding
- more storms and hurricanes
- some species may become extinct, others would shift to new zones
Climate change Bangladesh
Bangladesh is a low-lying country that is already suffering problems from coastal and river flooding, which is not helped by its very large and very poor population, making it extremely vulnerable to climate change. Climate change will affect Bangladesh both environmentally and economically..
- Already severe river flooding would become worse from heavier rainfall and sea level rise
- Tropical storms could become more of a common occurrence, and possibly do more destruction if it were to move further inland
- The dry season is already getting longer and this could cause more droughts.
- A small rise in sea levels could massively impact upon Bangladesh's farmland and agricultural output
- More river flooding could cause damage to people's homes and more disruption to lives and the economy
- Shrimp farming is very important but rising sea temperatures may damage this form of aquaculture
- Increased flooding will increase the spread of water-borne diseases.