Science & Impacts of Climate Change

There is broad consensus amongst scientists and politicians that if we are to avoid the full impact of climate change, which include increased floods and drought, reduced water availability and quality, extreme heat and other weather events, and rising rates of infectious diseases, we need to reduce global greenhouse emissions by at least 60 percent by 2050.

Climate change is an issue that no responsible political leader can ignore, particularly city leaders. Not only are cities a significant contributor to global greenhouse gas emissions, most cities also stand to be significantly affected by the dangerous impacts of climate change.

SCIENCE

The Greenhouse Effect
The Earth receives energy from the sun in the form of shortwave radiation. This is largely absorbed by the earth and reradiated back out towards space at much longer wavelengths. This long wave radiation is absorbed by greenhouse gases such as CO2 and keeps the earth warm. More greenhouse gases mean more warming.

Recorded Carbon Dioxide (CO2) Increases Greenhouse gases have been rising since the onset of the industrial revolution and are currently 381 parts per million (ppm) compared to a pre-1850 concentration of 280 ppm.

Projected Carbon Dioxide (CO2) Increases Greenhouse gases are predicted to continue rising over the coming century. Some projections put the CO2 concentration by 2100 as high as 950 ppm, an increase of 670 ppm.

Recorded Temperature Increases
Over the 20th Century global average surface temperatures have increased by 0.6°C but some locations have witnessed a local increase in excess of 2°C.

Projected Temperature Increases
This increase in CO2 concentration is predicted to cause an increase in global air temperature of between 1.4°C to 5.8°C. An average rise of 2°C is accepted by many as the threshold for unacceptable and unpredictable impacts on the planet.

IMPACTS

Economic
In October 2006 Sir Nicholas Stern, former Chief Economist and Senior VP for the World Bank summarized the economics of climate change in a new report. Stern stated that failure to tackle climate change could cost the world up to 7 trillion dollars.

Food and Water
Climate change will cause food and water shortages in certain areas. For example, rice production in China is predicted to fall one fifth by 2080. Two out of every three people in the world will be facing water shortages by 2025.

Extreme Weather
The frequency of extreme weather events is predicted to increase and there is evidence of this occurring already. The 2005 hurricane season broke virtually every record including 27 named storms and the strongest hurricane ever recorded in the Atlantic Basin.

Health
Climate change will increase the incidence of deaths from extreme weather events and disease. A rise in temperature of 2-3°C could increase the number of people at risk of malaria by around 3-5%, which is several hundred million people.

Sea Level Rise
Virtually every glacier in the world has been retreating over the past century. Both the Greenland and Antarctic ice caps are now losing a combined 20 billion tons of ice to the oceans each year. Sea level is predicted to rise by up to 0.88m by 2100. Over 17 million people in Bangladesh live at an elevation of less than 1.5m above sea level. The Pacific island nation of Tuvalu has already drawn up evacuation plans with New Zealand amid concerns of inundation by the sea.

The Gulf Stream Collapse
The Gulf Stream (also known as the thermohaline circulation) transports the equivalent heat output of a million power stations and warms the climate by up to 5°C in northwest Europe. Due to increased runoff from high latitude rivers and increased freshwater input from melting ice there is a possibility this oceanic current may collapse. There is already evidence it is beginning to weaken.

Nature
Enormous vegetation changes are predicted to occur. This will have an impact on biodiversity and a recent study has found that climate change threatens more than 1 million species with extinction by 2050.