Global climate

Earths atmopshere receives a constant input of solar radiation (insolation). In recent history there has been a relative balance between the insolation received and the energy re-radiated back out to space - which has kept the atmospheric temperatures stable.

Approximately 30% of the insolation is reflected back out to space - most by the clouds, but about 5% by the earths surface (.

About 45% of insolation is absorbed by the earths surface - which heats the ground and oceans. Some of this heat is tranfered into the atmosphere by convection through gases in the air. Most of the energy is emitted as long-wave radiation, some of which passes out into space, but some of which is absorbed by greenhouse gases in the atmosphere or re-radiated back towards the earths surface.

The natural greenhouse effect

The greenhouse effect is the process described above - in which gases in the atmosphere trap long-wave radiation emitted by the earths surface and contribute to a warming of the atmosphere.

This is a natural process that is vital for life on earth to exist, since without it the climate would be too cold. The main greenhouse gases are:

1. Water vapour: the most abundant of the greenhouse gases
2. Carbon dioxide: released mostly through burning of fossil fuels and forests but also volcanic erruptions.
3. Methane: released by animals and decaying vegetation, more effective than carbon dioxide.
4. CFCs: man-made chemeicals which are vastly more effective at trapping long-wave radiation than both CO² and methane.

The enhanced greenhouse effect

This refers to the principle that human activity is adding significant additional quantities of the greenhouse gases to the atmosphere and enhancing (accelerating) the natural process. This is disrupting the natural balance and leading to a relatively rapid warming of the atmosphere.

Positive feedback loops

Feedback that amplifies or increases change; it leads to exponential deviation away from an equilibrium. Positive feedback creates instability in systems.

• In the diagram an increase in gobal temperatures leads to melting of sea ice.
• The loss of white reflective surfaces reduces the albedo rate which results in the exposed darker surfaces of the oceans absorbing more solar energy which raises global temperatures and peretuates the process.
• This system will get further and further from the inital point of equilibrium.

Task

1. Draw a feedback chart to show the impact of the increasing methane being released from decaying vegetation in thawing permafrost

Negative feedback loops

Feedback that tends to damp down, neutralize or counteract any deviation from an equilibrium, and promotes stability. Negative feedback creates more stability in systems.

• In the diagram an increase in carbon dioxide leads to increased atmopsheric temperatures.
• This in turn leads to higher rates of photosythesis which results in more carbon dioxide being removed from the atmosphere and therefore counteracting the rise in temperature.

Global dimming refers to the theory that increased levels of atmospheric pollution have been having a cooling effect of the planets atmosphere.

The unprecedented grounding of all aircraft after the terrorist attacks on the World Trade Center in 2001 led to a rise in temperature. Scientists believe that the pollution particles in the air act as condensation nuclei around which water droplets form (clouds). Polluted air is leading to clouds having more small water droplets in them which reflect a higher proportion of insolation back out to space.

Pan-evaporation studies have shown decreasing levels of solar radiation reaching the earths surface in most places over that half century.

Who is releasing the most gases and why?

The major sources of greenhouse gas emissions are well known but reducing them appears to be a difficult process. The polluting countries are not neccessarily the ones that are suffering the worst effects of climate change. In addition, historically countries have created huge amounts of air pollution on the road to development yet NICs (newly industrialised countries) are being told not to do the same.

Tasks

1. Study fig 2.6 - interactive infographic (use fig 2.7 if on mobile device):
2. Take the top 10 emitters and suggest reasons for the high levels of pollution (dont just state the labels - think about why these countries need such high levels of energy generation etc).
3. Explain the impact of industrialisation on greenhouse emissions.
4. How has globalisation led to increased greenhouse gas emissions?

1. Open this link: http://www.wri.org//blog/2014/05/history-carbon-dioxide-emissions
2. Scroll down the the graph titled: 1960-2011: Per Capita Emissions in the West—Stable, but High
3. Describe the pattern shown - (who are the main producers of carbon dioxide/capita and how have their emissions changed over time?)
4. Now scroll to the graph titled: 1990s-2011: The Rise of Asia
5. Describe the pattern shown - (who are the main producers and how has it changed over time)
6. Describe the main differences between the two graphs.
7. Explain the differences shown.
8. In your opinion - which countries are most responsible for the high levels of carbon dioxide in the atmosphere.
9. With reference to the first graph - what are the implications for carbon dioxide emissions of rising standards of living in Asian countries.

Changes in sea ice

Tasks

1. Describe the pattern of sea ice minimum shown in fig 2.7.
2. Go to this page: nasa.gov and watch the video showing ice coverage at the artic.
3. Read the BBC article embedded below

Rising sea levels

Global sea levels are rising at apporoximately an eigth of an inch per year, and have risen roughly 8 inches over the last century. Sea levels rise for two main reasons:

1. Thermal expansion of the water as the sea temperatures rise
2. Increased melting of land based glaciers which adds additional water to the seas and oceans.

Tasks

1. Read this Independent article, answer the following questions
• Screen shot the map showing the regional location of Tuvalu
• Why is Tuvalu at such risk if sea levels continue to rise?
• Explain why the islands that have the most inhabitants on are the ones most at risk of flooding.
• How do the islands adapt naturally to sea level rise according to the article?

Changes in mountain ice

Switzerland relies on the water stored in its mountain glaciers. Dams store the meltwater released throughout the year to provide water for drinking, irrigation, industry and power generation.

Tasks

1. Read this Independent article, answer the following questions
• How many of Switzerlands glaciers are shrinking?
• What % of Switzerlands energy is produced by hydropower
• Explain why Switzerland can expect more water for hydropower over the next couple of decades.
• Describe how are they planning to cope with the eventual depletion of glacial meltwater

Changes in Carbon Storage

Before the industrial revolution, much of the worlds carbon was stored underground in rocks and fossil fuels. Humans have been releasing far more of these stores of carbon than would occur naturally. This has led to much higher concentrations of carbon dioxide in the atmosphere.
Higher concentrations of carbon dioxide in the atmosphere are leading to increased acidification of the oceans.

Tasks

1. Use this National Geographic article in fig 2.10 to describe how the oceans are becoming increasingly acidic.
2. Outline the two main reasons mentioned about why scientists are concerned about increasing acidification.

Changes in Biomes

Use the article in figure 2.10 to describe the patterns of species migration predicted due to climate change.

Changes in Agriculture

Open the article (fig 2.11) and scroll down to the section titled: Climate change affects agriculture.

Tasks

1. Read and then describe in your own words the impact of climate change on:
   • growing seasons
   • spread of insects & diseases
   • fish stocks

Changes in mountain ice

Switzerland relies on the water stored in its mountain glaciers. Dams store the meltwater released throughout the year to provide water for drinking, irrigation, industry and power generation.

Tasks

1. Read this Independent article, answer the following questions
• How many of Switzerlands glaciers are shrinking?
• What % of Switzerlands energy is produced by hydropower
• Explain why Switzerland can expect more water for hydropower over the next couple of decades.
• Describe how are they planning to cope with the eventual depletion of glacial meltwater

Responding to rising sea levels

Read this National Geography article, answer the following questions