1 The greenhouse effect and climatic extremes
1.1 Introduction
Concentrations of carbon dioxide (CO2) in the atmosphere have increased from pre-industrial levels of about 270 μmol mol−1 to current concentrations of 360 μmol mol−1. Increases in greenhouse gases in the atmosphere, such as CO2, methane and nitrous oxide, are predicted to result in a rise in mean temperatures of 2–3°C by the year 2050 and even by as much as 4.5°C by 2100 AD together with more frequent episodes of water deficit and higher temperature events.
In the future it is thought that the increase in CO2 and other greenhouse gases will cause an increase in global mean temperature, with larger increases at high latitudes than elsewhere and larger increases during winter than summer.
Via various models, scientists have predicted that, for the UK, there is in all seasons and for all scenarios a southeast to northwest gradient across the UK in the overall magnitude of the climate warming, with the southeast warming more rapidly than the northwest.
Web-based resources on climate change and impacts on agriculture:
BBC Weather Centre covers the basics of climate change science
BBC Weather Centre on extreme weather
BBC News covers the heatwave of 2003
UK's Climate Impact Programme considers UK agriculture and climate change
UK's Climate Impact Programme on observed UK climate trends
University of Reading website on agriculture and climate change
Environmental Change Institute podcasts
Activity 1
If you are a gardener, think about your own observations of growing and harvesting the fruits of your labour, e.g. vegetable crops in your locality. Have you noticed anything about their yield under different climates, seasonable changes, etc.? Make a note of this and discuss with a friend what you have observed.
Learning outcomes