Climate Change: Carbon footprints and cycles

Climate Change: Carbon footprints and cycles

What is climate change? • What do you think climate change is?

• What do we actually mean when we talk about climate?

• How is it measured?

• What affects it?

• What effect is climate change having?

• What can we do about it?

Climate Change: Carbon footprints and cycles

How has the global temperature changed?

Temperatures over the last 400 000 years obtained from the Vostok ice core, the longest continuous ice-

core record to date

Climate Change: Carbon footprints and cycles

Variations of the mean surface temperature during the last 140 years:

Climate Change: Carbon footprints and cycles

What questions should you be asking when presented with data like this?

• Where are the observations made? (in towns, open countryside, at sea; developed countries only or mostly northern hemisphere?)• How are the measurements made? (is a daily average taken, or highest temp of the day, are night time temperatures included)• What instruments are used? And how are they calibrated?• How are the global averages calculated?

Climate Change: Carbon footprints and cycles

What affects the climate?• The Earth’s surface is warmer than we might expect considering the

amount of radiation reaching us from the sun.

• Some gases in the atmosphere absorb infrared radiation that has been emitted by the surface.

• These gases occur naturally in the atmosphere so our planet is warmer than expected and can support life.

Climate Change: Carbon footprints and cycles

Greenhouse gases

- So what are these greenhouse gases?

Water vapour; carbon dioxide; methane; nitrous oxide and ozone.

- How do greenhouse gases absorb the infrared radiation?

Climate Change: Carbon footprints and cycles

This table shows changes in concentrations of the key natural greenhouse gases and some synthetic gases (halocarbons that are now banned)

Climate Change: Carbon footprints and cycles

Effect on global climate

• How do we know that human activities are having an effect on climate?

• Scientists use models to simulate the Earth’s temperature variations and to predict what may happen in the future.

• This diagram shows observed temperatures (red) and modelled predictions of the Earth’s temperature over the last 140 years.

Climate Change: Carbon footprints and cycles

The carbon cycle Anthropogenic versus natural carbon emissions

The natural carbon cycle:

Climate Change: Carbon footprints and cycles

• Green arrows – terrestrial cycle (short time-scale, moths/years to decades)• Photosynthesis by green plants removes CO2 from the atmosphere (CO2

that isn’t respired is ‘fixed’ carbon)• Respiration of plants returns CO2 to the atmosphere• Transfer of fixed carbon to the store of dead organic matter in soil and

detritus• Carbon returned to the atmosphere by decomposition (respiration of

decomposers and detritivores)• Blue Arrows – oceanic cycle (intermediate time-scale, up to 1000 years)• CO2 dissolves into surface waters (dissolved inorganic carbon, DIC)• CO2 outgases from the ocean (E and F are approximately balanced)• Fixed carbon exported to deep ocean (planktonic debris, faecal pellets of

animals and other detritus)• Upward movement of deep DIC-rich water• Sinking of lower-DIC content surface waters• Brown arrows – long-term geological cycle (hundreds of millions of years)

Climate Change: Carbon footprints and cycles

Anthropogenic CO2

The global budget of CO2 for the 1980s showing average annual values in GtC y-1.

Climate Change: Carbon footprints and cycles

• The two main anthropogenic sources of CO2 are: – burning fossil fuels and – changing land use (nearly 90% attributed to loss of carbon from

forest ecosystems) • So how much CO2 has been released to the atmosphere due to

human activities during the last 200 years or so? (major period of industrialisation)

Climate Change: Carbon footprints and cycles

Carbon footprints• What do you think should be taken into account when

calculating your carbon footprint? • Now take a look at the carbon calculator.

Climate Change: Carbon footprints and cycles

Reducing emissions• How might you reduce emissions of carbon dioxide?

(on a personal level rather than industrially based)• Think about what you now know about the carbon cycle and

what affects your footprint?

Climate Change: Carbon footprints and cycles

Further Resources• If you have found this session interesting why not try a course with

the Open University

• Please go to www3.open.ac.uk/study for further details or call 44(0) 845 300 60 90

• http://climateprediction.net/ – a project launched in September 2003 to explore the uncertainty in climate model predictions by using ‘distributed’ computing.

• Calculate your carbon footprint online at:

– http://www.bp.com/iframe.do?categoryId=9032780&contentId=7060112

– http://www.safeclimate.net/calculator/