The document discusses the impacts of a 4°C rise in global temperatures according to a map produced by the Met Office. A 4°C rise would have severe consequences including decreased agricultural yields, less available water for over 1 billion people, risks from sea level rise and coastal flooding affecting millions, and increased extreme weather events. However, taking strong action to reduce emissions could limit warming to 2°C, significantly reducing these severe risks. The document aims to show decision-makers at the Copenhagen climate negotiations the high stakes of limiting warming to less than 4°C.

1. Effects of ‘high-end’ climate change
The impacts of climate change will be widespread across the globe. Emissions of
greenhouse gases have already altered the Earth’s atmosphere and the climate is already
changing. We will live with the consequences of these changes for the next few
decades, regardless of the actions we take now to reduce our emissions.
However, as Kirsty Lewis, Principal Climate Change Consultant, explains beyond that
time, future climate change depends on whether we continue to emit greenhouse gases
into the atmosphere at the rate we currently do, or whether we take effective steps to
dramatically reduce our emissions.
The difference between these two courses of action is the difference between some
inevitable climate change, and more severe, ‘high-end’ climate change in the longer
term. This is a decision that faces politicians at the global climate change negotiations at
Copenhagen in December.
Mapping the impacts
In order to understand more about what the human impact of high-end climate change
might be, and, therefore, what would happen if a successful agreement can not be
reached at Copenhagen, the Met Office Hadley Centre has produced a map outlining
some of the impacts that may occur if the global average temperature rises by 4 °C
(7 °F) above the pre-industrial climate average.
The map was produced by the Met Office (on behalf of HM Government), but contains
contributions from climate scientists from other institutions conducting the latest
research on climate impacts.
Although the average temperature rise over the globe is 4 °C (7 °F) the projection on the
map shows that this average rise will not be spread uniformly across the globe. The land
will heat up more quickly than the sea, and high latitudes, particularly the Arctic, will
have larger temperature increases. The average land temperature will be 5.5 °C above
pre-industrial levels.
IN THIS LINK YOU CAN SEE AND GET SURPRISE
WHAT IS GOING TO HAPPEN IF THE TEMPARATURE INCREASE
4 °C (7°F):
http://www.actoncopenhagen.decc.gov.uk/content/en/embeds/flash/4-
degrees-large-map-final
Human impacts
The impacts on human activity shown on the map are only a selection of those that may
occur, and highlight the severe effects on water availability, agricultural productivity,
extreme temperatures and drought, the risk of forest fire and sea level rise.

2. • Agricultural yields are expected to decrease for all major cereal crops in all
major regions of production.
• The availability of water will be affected by melting of glaciers, particularly in
areas such as the Indus basin and western China, where much of the river flow
comes from melt water.
• Population increases, combined with changes in river run-off as a result of
changes in rainfall patterns and increased temperatures, could mean that by 2080
significantly less water is available to approximately one billion people already
living under water stress.
• For many areas of the world sea-level rise, combined with the effect of storms,
will threaten low-lying coastal communities. There are often very dense
populations living along coasts, as well as important infrastructure and high-
value agricultural land, which makes the impact of coastal flooding particularly
severe. The intrusion of salt water on farming land, and the risk to lives of
flooding events could affect millions of people worldwide every year.
The impacts on the poster are frightening, and the list is not exhaustive. However, the
map represents a world where climate change has gone unmitigated, where we have
continued to emit greenhouse gases at the rates we are today. If we continue to do this,
then the likelihood of the planet warming by 4 °C (7 °F) increases, and as it does, so the
risk of these impacts being realised also increases.
By taking strong and effective action to curb greenhouse gas emissions, it may be
possible to limit this temperature rise to 2 °C (4 °F). Although this would still bring
some adverse impacts, the risk of the very severest impacts, as shown in the Met Office
map, is significantly reduced.