Environmental Essay no.29 – Adapting to the Climate of the Future

Compared to other places in the world, it seems that the effects of climate change will be fairly modest in Northern Europe. According to the UN Climate Panel, the IPCC (the Intergovernmental Panel on Climate Change), which counts climate experts from all over the world, temperature increases will probably be twice as big for instance in the Arctic as it is in Northern Europe.

Nevertheless, in Europe as a whole there is a risk of for instance drought, with serious implications for agriculture and severe forest fires, especially in the Mediterranean area.

Table 1 Climate change in Denmark Possible climate change in Denmark up to the year 2100, based on an average scenario (according to DMI)

Temperature increase	+ 3-5 °C
Summer precipitation	-10-25 %
Extreme summer precipitation	+ 10-20 %
Winter precipitation	+ 20-40 %
Winter precipitation, snow	- 70-90 %
Sea-level rise	+ 0.5 m

Storm activity Moderate increase The figures represent an average scenario for Denmark, which predicts a possible general warming of approx. 3-5°C within a number of decades. Warming is seen mainly for night temperatures, thus reducing the diurnal temperature range, compared to what we are used to. Spring will tend to come earlier, and autumn later. Migratory birds will arrive earlier, forest trees will leaf earlier. Generally, precipitation will increase by 10-20 per cent annually – with less rain in summer, more intense precipitation episodes, and longer periods without precipitation. There is also a tendency towards more storm activity.

Although we live in the part of the World where the impact of climate change will be less extreme, we should still anticipate that we may be affected, mainly because Denmark is a low-lying country with a coastline of more than 7,000 km, and several hundred small islands. The sea level will rise generally, the annual variations in water levels in watercourses will increase, and the increasing sea level will affect the coastline, which is at risk of retreating. There is also a risk of intrusion of salt in groundwater near the coasts.

To enable us to adapt to the new situation in the best possible way, knowledge on the possible development of the climate in Denmark is essential. We should therefore start integrating the probable climate change in existing practices at state, regional and local levels, and where otherwise relevant.

The DMI is working with climate change
In Denmark climate change is researched primarily at the Danish Meteorological Institute, the DMI. The DMI is monitoring the climate and taking part in international climate research, which constantly tries to assess possible future climate change.

On the basis of international scientific work, the DMI has also calculated how the climate will change in Denmark in the future. The work by DMI has resulted in the establishment of different scenarios, i.e. possible developments of the climate under specific conditions – and, thus, not the same as prognoses.

Change of temperature(°C)

Figure 1 Climate change over the next century Projections of global temperature rises and water-level rises in scenarios from the UN Climate Panel, the Intergovernmental Panel on Climate Change. The curves represent a number of different scenarios. The extent of changes varies, but the trend is the same.

(According to: IPCC, 2001)

The data in table 1 are a popular representation of one of the DMI climate scenarios for Denmark – at this moment one of the best forecasts of climate change to be expected in response to global warming.

The results from the DMI are based on couplings of large global climate models with the more complex regional models, which are also used for weather forecasts, although in a different form. The global climate models are the same as those used by for instance the UN Climate Panel to make projections of the global climate (see figure 1).

The average scenario presented for Denmark is of course subject to great uncertainty – both as regards the assumptions underlying the calculations, and as regards the calculations proper. Therefore the development might not be exactly as predicted in the scenario. What we can say is that the temperature trends are almost identical, no matter which scenarios for Denmark we are looking at. Variations are primarily a matter of magnitude – or the extent of changes. The uncertainty is greater for precipitation, and for changes in storm activity in particular. The tendency towards less precipitation in the summer and more in the winter, and towards more intense precipitation incidents is, however, generally found also in other modelling systems than those applied by the DMI.

Ocean currents – a joker
The strong Atlantic Ocean currents, bringing warm water to the North and thus acting like a sort of heater, are very important for the climate in Europe and the Arctic. The most important currents are temperature- and salt-induced currents, but currents may also be wind-driven. The Gulf Stream is part of this system of ocean currents. Most climate model calculations show that total disruption of these currents as a result of global warming is fairly improbable. But according to the calculations, their power will be significantly reduced.

You might think that – on the face of it – this would cause temperature decreases in the Arctic and in Northern Europe, as has probably happened so often during the last Ice Age. But – when the climate is warmer, as it is today – sea-ice, clouds and water vapour have a much larger moderating impact on energy balances than they had during the glacial ages. Therefore the impact of weakening sea currents is more than offset, so that the largest temperature rises are actually seen in the Arctic. Also for Northern Europe, calculations indicate rising temperatures even if the heat transport in the Atlantic Ocean is decreasing.

Strandvejen - the coastal road north of Copenhagen

A general sea-level rise will not only increase the risk of storm surge of low-lying land. It will also cause increased coastal erosion and retreating coastlines. In some areas that are protected against erosion today, the beaches may disappear, and the protective measures may be undermined. Pathways along the beach may be more difficult to use.

(Photo: Danish Coastal Authority)

The Danish climate in the future