It was the summer, scientists now realise, when global
warming at last made itself unmistakably felt. We knew that summer 2003 was remarkable:
Britain experienced its record high temperature and continental Europe saw forest fires
raging out of control, great rivers drying to a trickle and thousands of heat-related
deaths. But just how remarkable is only now becoming clear.
The three months of June, July and August were the warmest
ever recorded in western and central Europe, with record national highs in Portugal,
Germany and Switzerland as well as in Britain. And they were the warmest by a very long
way. Over a great rectangular block of the earth stretching from west of Paris to
northern Italy, taking in Switzerland and southern Germany, the average temperature for the summer months was 3.78°C above the long-term norm,
said the Climatic Research Unit (CRU) of the University of East Anglia in Norwich, which
is one of the world's leading institutions for the monitoring and analysis of
temperature records.
That excess might not seem a lot until you are aware of the
context - but then you realise it is enormous. There is nothing like this in previous
data, anywhere. It is considered so exceptional that Professor Phil Jones, the CRU's
director, is prepared to say openly - in a way few scientists have done before - that the 2003 extreme may be directly attributed, not to natural climate variability,
but to global warming caused by human actions.
Meteorologists have hitherto contented themselves with the
formula that recent high temperatures are “consistent with predictions” of climate
change. For the great block of the map - that stretching between 35-50N and 0-20E - the
CRU has reliable temperature records dating back to 1781.
Using as a baseline the average summer temperature recorded between 1961 and 1990,
departures from the temperature norm, or “anomalies”, over the area as a whole can
easily be plotted. As the graph shows, such is the variability of our climate that over
the past 200 years, there have been at least half a dozen anomalies, in terms of excess
temperature - the peaks on the graph denoting very hot years - approaching, or even
exceeding, 2°C. But there has been nothing remotely like 2003, when the anomaly is
nearly four degrees.
“This is quite remarkable,' Professor Jones told The
Independent. “It's very unusual in a statistical sense. If this series had a normal
statistical distribution, you wouldn't get this number. The return period [how often it
could be expected to recur] would be something like one in a thousand years. If we look
at an excess above the average of nearly four degrees, then perhaps nearly three degrees
of that is natural variability, because we've seen that in past summers. But the final
degree of it is likely to be due to global warming, caused by human actions.”
The summer of 2003 has, in a sense, been one that climate
scientists have long been expecting. Until now, the warming has been manifesting itself mainly in winters that have been less cold than in summers that have been much hotter.
Last week, the United Nations predicted that winters were warming so quickly that winter
sports would die out in Europe's lower-level ski resorts. But sooner or later, the
unprecedented hot summer was bound to come, and this year it did.
One of the most dramatic features of the summer was the hot
nights, especially in the first half of August. In Paris, the temperature never dropped
below 23°C (73.4°F) at all between 7 and 14 August, and the city recorded its
warmest-ever night on 11-12 August, when the mercury did not drop below 25.5°C (77.9°F).
Germany recorded its warmest-ever night at Weinbiet in the Rhine Valley with a lowest
figure of 27.6°C (80.6°F) on 13 August, and similar record-breaking nighttime
temperatures were recorded in Switzerland and Italy.
The 15,000 excess deaths in France during August, compared with previous
years, have been related to the high night-time temperatures. The number gradually
increased during the first 12 days of the month, peaking at about 2,000 per day on the
night of 12-13 August, then fell off dramatically after 14 August when the minimum
temperatures fell by about 5°C. The elderly were most affected, with a 70 per cent
increase in mortality rate in those aged 75-94.
For Britain, the year as a whole is likely to be the warmest
ever recorded, but despite the high temperature record on 10 August, the summer itself -
defined as the June, July and August period - still comes behind 1976 and 1995, when there were longer periods
of intense heat. “At the moment, the year is on course to be the third hottest ever in
the global temperature record, which goes back to 1856, behind 1998 and 2002, but when all the records for
October, November and December are collated, it might move into second place,' Professor
Jones said. The ten hottest years in the record have all now occurred since 1990. Professor Jones is in no doubt about the
astonishing nature of European summer of 2003. “The temperatures recorded were out of
all proportion to the previous record," he said.
“It was the warmest summer in the past 500 years and
probably way beyond that. It was enormously exceptional."
His colleagues at the University of East Anglia's Tyndall
Centre for Climate Change Research are now planning a special study of it. “It was a
summer that has not been experienced before, either in terms of the temperature extremes
that were reached, or the range and diversity of the impacts of the extreme heat," said
the centre's executive director, Professor Mike Hulme.
“It will certainly have left its mark on a number of
countries, as to how they think and plan for climate change in the future, much as the
2000 floods have revolutionised the way the
Government is thinking about flooding in the UK. The 2003 heatwave will have similar repercussions across Europe."