Weather: Short term, day to day changes in the atmosphere.
Climate: The average weather conditions over 30 years.
Interglacials: Warm periods.
Glacials: Cold periods, ice ages, ice sheets 400-3000m thick extended across the Northern Hemisphere.
We know climate was different in the past because:
- Fossils of animals and plants that no longer live in the UK.
- Landforms left by glaciers.
- Samples from ice sheets in Antarctica. Ice sheets are made up of layers of ice, a layer for each year. Air bubbles are trapped in the ice sheets. Climatologists study the CO2 levels to reconstruct past climates.
Recent climate change
We know climate has changed in the more recent past because of:
- Old photos, paintings
- Recorded dates of blossom and migration of birds
Past climate change theories
Very large and explosive volcanic eruptions change earths climate. Ash and gas spread around the stratosphere and stop sunlight reaching the erths surface, cools the earth.
e.g. Mt Pinatuba 1991, Philippines: reduced global sunlight by 10% and cooled the earth 0.5 degrees for a year.
Black areas on the suns surface. Sometimes there are more and then they disappear. Spots mean greater activity and more solar energy being sent toward the Earth, making it warmer.
- Changes in the way the Earth orbits the sun from circular to ellipse alters the amount of sunlight the Earth recieves.
- The Earths axis also moves and wobbles about affecting how much sunlight is recieved.
In 982 'Erik the red' was banished to Greenland. He and about 500 other vikings found a patch of land that was largely free of ice. This was at the start of the Medieval warm period. The warmer climate meant:
- They had over 200 farms, keeping goats, sheep and cows, and growing hay to feed the animals.
- A population of 3000-4000 vikings.
- Trade links with Iceland and Norway.
- Summer hunting expeditions North of the Arctic circle, for seas and Whales.
They died out soon after 1410 they died out because the little ice age made life impossible for the greenland vikings. They ran out of food and died out, however they did not help their own survival:
- Deforestation and soil erosion meant that the viking farms produced very little food. They had damaged the land they were dependant on.
- The had depended too much on trade with Iceland and Norway. When this stopped because of sea ice they had no one else to turn to.
- They were not very adaptable. They tried to live as they did in Norway and Iceland.
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.
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 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
The UKs climate
- 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
In 2008, global CO2 levels reached 380ppm (parts per million) 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
It is hard to predict future climate because:
- What the population will be
- If we will continue to use fossil fuels or will change to cleaner fuels
- If we will change our lifestyles
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.