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Extreme will become normal

​The UN’s new climate report summarises all our current knowledge about climate change. Researchers are now 95 per cent sure that global warming is caused by human activity.

The Intergovernmental Panel on Climate Change (IPCC) will present its report by the end of 2014, but published its first interim report in September last year. The interim report addresses scientific evidence for the climate problem.

“There is not that much new information in the interim report, but it confirms what emerged from the previous report, i.e. that climate change is caused by human activity. Now we are more certain than ever,” says Professor Inger Hanssen-Bauer, Head of the Climate Service Centre at the Norwegian Meteorological Institute.

She explains that increasing temperatures intensify the hydrological cycle. Higher temperatures enable the air to hold more water, which then falls as precipitation.

On the equator, the earth absorbs more energy than it emits, whereas the opposite is the case at the poles. This creates an energy surplus on the equator, and a deficit at the poles. This is evened out as warm air and warm water flow towards higher latitudes, whereas cold winds and currents go in the opposite direction.

“This is referred to as general circulation. It is uncertain what impact global warming has on general circulation. However, it could cause a shift in the polar front – and we are increasingly sure that it is migrating towards higher latitudes,” Hanssen-Bauer says.

The signals show a clear increase in mean temperature and precipitation. Towards the middle or end of the century, what may seem like extreme years or seasons now, will become normal, and we need to raise awareness of this.

Professor Inger Hanssen-Bauer, Head of the Climate Service Centre at the Norwegian Meteorological Institute

Warmer, wetter, wilder

We often hear that the climate is becoming warmer, wetter and wilder.

“Warmer? Yes. Wetter? Yes, Norway will probably become wetter. But wilder? It is not very likely that it will be more windy everywhere, but storm tracks may shift. Local effects of global warming may then be that winds and storms come from different directions than we are used to. We have already seen examples of storms that suddenly come from a different direction. The same is the case for, for instance, avalanches,” Hanssen-Bauer says.

Furthermore, global warming may also cause higher precipitation. This will be the biggest problem in Norway, according to Professor Hanssen-Bauer.

“If we experience heavy precipitation in urban areas over a short period, where there are a lot of paved roads etc. the water must be drained off. We must then make sure that it doesn’t all go into the sewer system at once, but is delayed by green roofs and retention basins,” Hanssen-Bauer continues.

The increase in precipitation will also affect the amount of snow, glaciers, evaporation and run-off. All this will in turn impact the ecosystems. Society must also adapt to all these changes.

“This means we must pick out the things we are becoming increasingly sure of. For Statnett, this could for instance be the risk of ice on power lines, electrical installations and monster pylons. Some years we may have a lot of wet, heavy snow, perhaps in areas where this has not been a problem previously, and it’s important that the installations are designed for this. The problem is that it can be difficult to predict exactly where we will have a problem,” Hanssen-Bauer says.

Professor Inger Hanssen-Bauer believes that Statnett must take climate challenges into account when building new facilities.

Robust signals

The clearest signals of climate change are a generally warmer climate, more precipitation at higher latitudes and higher sea level. Some areas of Norway are protected against a rise in sea levels due to continued land rising following the last ice age, whereas other areas are more vulnerable, particularly outer coastal areas of South-Western Norway and in Northern Norway. Here sea levels may rise by more than half a metre – even more in the case of flooding.

“Combined with heavy precipitation, this could cause major problems, which we must account for in our planning, particularly where rivers run into the sea,” Hanssen-Bauer emphasises. In the last 50 years, we have seen clear signals of climate change causing more extreme precipitation.

“The signals show a clear increase in mean temperature and precipitation. Towards the middle or end of the century, what may seem like extreme years or seasons now, will become normal, and we need to raise awareness of this,” says the researcher.

On 22 January, The European Commission presented a proposal for a new climate and energy framework for the period 2020-2030. They propose a reduction in the emission of greenhouse gases of 40 per cent, a renewable energy target at EU level of 27 per cent and climate quota reforms. The Norwegian authorities will work closely with the EU on the development of the 2030 framework.

Text: Sissel Fantoft Photo: Bo Mathisen

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