Climate science

Europe may experience higher warming than global average

New research predicts that temperatures greater than the 2 °C global average will be experienced in Northern and Eastern Europe in winter and Southern Europe in summer; however, North-Western Europe -- specifically the UK -- will experience a lower relative warming.

Date: March 6, 2014

Source: Institute of Physics

The majority of Europe will experience higher warming than the global average if surface temperatures rise to 2 degrees C above pre-industrial levels, according to a new study.

Science Daily,

7 March, 2014

The majority of Europe will experience higher warming than the global average if surface temperatures rise to 2 °C above pre-industrial levels, according to a new study published today.

Under such a scenario, temperatures greater than the 2 °C global average will be experienced in Northern and Eastern Europe in winter and Southern Europe in summer; however, North-Western Europe -- specifically the UK -- will experience a lower relative warming.

The study, which has been published today, 7 March, in IOP Publishing's journal Environmental Research Letters, also shows that in the summer, daily maximum temperatures could increase by 3-4 °C over South-Eastern Europe and the Iberian Peninsula and rise well above 40 °C in regions that already experience some of the highest temperatures in Europe, such as Spain, Portugal and France. Such higher temperatures will increase evaporation and drought.

In the winter, the maximum daily temperatures could increase by more than 6 °C across Scandinavia and Russia.

Lead author of the research Robert Vautard, from Laboratoire des Sciences du Climat et de l'Environnement (CEA/CNRS/UVSQ), said: "The 2 °C warming target has mainly been decided among nations as a limit not to exceed in order to avoid possibly dangerous climate change. However, the consequences of such a warming, at the scale of a continent like Europe, have not yet been quantified.

"We find that, even for such an ambitious target as 2 °C, changes in European climate are significant and will lead to significant impacts."

The study also shows that there will be a robust increase in precipitation over Central and Northern Europe in the winter and Northern Europe in the summer, and that most of the continent will experience an increase in instances of extreme precipitation, increasing the flood risks which are already having significant economic consequences.

Southern Europe is an exception, and will experience a general decline in mean precipitation.

To arrive at their conclusions, the researchers used an ensemble of 15 regional climate models to simulate climate changes under an A1B scenario, which represents rapid economic growth and a balanced approach to energy sources.

In addition to temperature and precipitation changes that may occur, the researchers also investigated atmospheric circulation and winds, but found no significant changes.

"Even if the 2 °C goal is achieved, Europe will experience impacts, and these are likely to exacerbate existing climate vulnerability. Further work on identifying key hotspots, potential impacts and advancing carefully planned adaptation is therefore needed," the researchers write in their study.

Story Source:

The above story is based on materials provided by Institute of Physics. Note: Materials may be edited for content and length.

Journal Reference:

Robert Vautard, Andreas Gobiet, Stefan Sobolowski, Erik Kjellström, Annemiek Stegehuis, Paul Watkiss, Thomas Mendlik, Oskar Landgren, Grigory Nikulin, Claas Teichmann, Daniela Jacob. The European climate under a 2 °C global warming. Environmental Research Letters, 2014; 9 (3): 034006 DOI: 10.1088/1748-9326/9/3/034006

Evidence for North Atlantic current shut-down ~120 ka ago

Earth Pages

7 March, 2014

A stupendous amount of heat is shifted by ocean-surface currents, so they have a major influence over regional climates. But they are just part of ocean circulation systems, the other being the movement of water in the deep ocean basins. One driver of this world-encompassing system is water density; a function of its temperature and salinity. Cold saline water forming at the surface tends to sink, the volume that does being replaced by surface flow towards the site of sinking: effectively, cold downwellings ‘drag’ major surface currents along. This is especially striking in the North Atlantic where sinking cold brines are focused in narrow zones between Canada and Greenland and between Greenland and Iceland. From there the cold water flows southwards towards the South Atlantic at depths between 1 and 5 km. The northward compensating surface flow, largely from tropical seas of the Caribbean, is the Gulf Stream/North Atlantic Current whose warming influence on climate of western and north-western Europe extends into the Arctic Ocean.

Circulation in the Atlantic Ocean. the orange and red water masses are those of the Gulf stream and North Atlantic Deep Water (credit: Science, Figure 1 in Galaasen et al. 2014)

 

Since the discovery of this top-to-bottom ‘conveyor system’ of ocean circulation oceanographers and climatologists have suspected that sudden climate shifts around the North Atlantic, such as the millennial Dansgaard-Oeschger eventsrecorded in the Greenland ice cores, may have been forced by circulation changes. The return to almost full glacial conditions during the Younger Dryas, while global climate was warming towards the interglacial conditions of the Holocene and present day, has been attributed to huge volumes of meltwater from the North American ice sheet entering the North Atlantic. By reducing surface salinity and density the deluge slowed or shut down the ‘conveyor’ for over a thousand years, thereby drastically cooling regional climate. Such drastic and potentially devastating events for humans in the region seem not to have occurred during the 11.5 thousand years since the end of the Younger Dryas. Yet their suspected cause, increased freshwater influx into the North Atlantic, continues with melting of the Greenland ice cap and reduction of the permanent sea-ice cover of the Arctic Ocean, particularly accelerated by global warming.

 

The Holocene interglacial has not yet come to completion, so checking what could happen in the North Atlantic region depends on studying previous interglacials, especially the previous one – the Eemian – from 130 to 114 ka. Unfortunately the high-resolution climate records from Greenland ice cores do not extend that far back. On top of that, more lengthy sea-floor sediment cores rarely have the time resolution to show detailed records, unless, that is, sediment accumulated quickly on the deep sea bed. One place that seems to have happened is just south of Greenland. Cores from there have been re-examined with an eye to charting the change in deep water temperature from unusually thick sediment sequences spanning the Eemian interglacial (Galaasen, E.V. and 7 others 2014. Rapid reductions in North Atlantic Deep Water during the peak of the last interglacial period. Science, v. 343, 1129-1132).

 

The approach taken by the consortium of scientiosts from Norway, the US, France and Britain was to analyse the carbon-isotope composition of the shells of foraminifers that lived in the very cold water of the ocean floor during the Eemian. The ratio of 13C to 12C, expressed as δ13C, fluctuates according to the isotopic composition of the water in which the forams lived. What show up in the 130-114 ka period are several major but short-lived falls in δ13C from the general level of what would then have been North Atlantic Deep Water (NADW). It seems that five times during the Eemian the flow of NADW slowed and perhaps stopped for periods of the order of a few hundred years. If so, then the warming influence of the Gulf Stream and North Atlantic Current would inevitably have waned through the same intervals. Confirmation of that comes from records of surface dwelling forams. This revelation should come as a warning: if purely natural shifts in currents and climate were able to perturb what had been assumed previously to be stable conditions during the last interglacial, what mightanthropogenic warming do in the next century?