Global warming

3. Recorded temperatures

Analyses of over 400 proxy climate series (from trees, corals, ice cores and historical records) show that the 1990s was the warmest decade of the millennium and the 20th century the warmest century. The warmest year of the millennium was 1998, and the coldest was probably 1601. (Climatic Research Unit, 2003)

Throughout historical times, fluctuations in the Earth's mean temperature have been recorded. During the seventeenth century, the Thames periodically froze over during winter and mini-glaciers were present in the North West Highlands of Scotland. More recently, the 1990s included some of the hottest years ever recorded in the British Isles, and 10 August 2003 was the hottest day ever on record. An annual temperature record for central England has been constructed, beginning in 1659.

Click on 'View document' to open a chart of central England temperatures from 1659 to 1995

View document

Look at the chart in the aboce document. How do the readings for 1660–1700 compare to 1960–2000?

You have probably noticed that in the first period most points were below the mean, but in the latter period, most were above it. Because the data are so scattered, some method is required for seeing the overall trend more clearly. A single ‘line of best fit’ (regression analysis) is not appropriate, as it hides small-scale variations that may be significant. Such changes in the recorded temperatures are manifest throughout the British Isles, resulting in changes to natural fauna and flora. These changes are also having local economic impact, such as the northwards spread of vineyards in the UK. (At the time of writing I believe the most northerly vineyard in the UK is in Swillington, near Leeds.)