Global warming takes time out

Refined climate forecasts predict less warming over the next few years

The observed, globally averaged surface temperature anomalies (annual average and smoothed) show, in addition to a positive trend, multidisciplinary variations. © Climate Research Unit / University of East Anglia
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More and more climate researchers have reported worldwide new temperature records in recent decades. According to a new Nature study, it could be over once in the next few years. The reason for this is a natural climate change, which is expected to alleviate the long-term warming trend in the coming decade.

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Climatologists from the Kiel Leibniz Institute for Marine Sciences (IFM-GEOMAR) and the Hamburg Max Planck Institute (MPI) for Meteorology have found this out using refined climate model forecasts.

"So that you understand us correctly, we do not posit that man-made climate change will not be as bad as feared, " explains Professor Mojib Latif of IFM-GEOMAR. "The generally upward trend is only superimposed by a long-period oscillation, which in the next few years could then lead to a net increase in temperature, " continues Latif.

"It's as if they are driving from the coast to the high mountains, crossing over foothills and valleys again and again, before they reach the summit, " says Johann Jungclaus from the MPI for Meteorology. "At the latest in a few years, when the trends of both phenomena complement each other, the temperatures will rise again more strongly." Display

Take into account fluctuations in ocean currents

Previous bills on global change, as published in the latest report of the 2007 UN Climate Change Council (IPCC), have been carried out assuming certain future atmospheric greenhouse gas developments. This strategy is justified as long as one is interested in the long-term development of the climate until about the end of this century.

To predict also the short-term development in the coming years, the models must receive additional information about the natural climatic fluctuations, in particular about the fluctuations of the ocean currents. The lack of appropriate measurements has hitherto prevented this.

Observed and simulated development of global averaged surface temperatures. Red: Observations, black: simulations without taking ocean observations into account, green: simulations with consideration of ocean observations. The vertical bars indicate the dispersion of the three forecasts. Climate Research Unit / University of East Anglia

Predict short-term climate variability

The scientists from IFM-GEOMAR and the MPI for Meteorology have now developed a method to derive sea currents from sea surface temperatures. The latter are well known for the past 50 years. With this additional information, climate models can be used to predict the short-term natural climatic fluctuations that superimpose long-term anthropogenic warming. The refined predictions suggest that global warming will weaken somewhat in the coming years.

Noel Keenlyside of the IFM-GEOMAR, Emmy-Noether Fellow and lead author of the new study, explains: "In addition to greenhouse gas concentrations, we have set the observed sea surface temperature of the last decades in our climate model, one Approach that we have already successfully used in season forecasting, such as the El Ni o forecast. Sea temperatures affect the winds and the heat exchange between the ocean and the atmosphere, and both factors in turn influence ocean currents

Christmas in Northern Germany?

And further: The results are very encouraging and show that, in addition to the global mean temperature, it is possible, at least for some regions of the world, to predict the natural, decadal climate variability. These areas also include Europe and North America, which are influenced by natural variability in the North Atlantic and tropical Pacific, respectively

Latif summarized the results as follows: With such forecasts, we will not tell them whether there is a white Christmas in Northern Germany in 2012, but can already indicate a tendency, whether certain decades rather above average warm or cold, unless other unpredictable effects, such as volcanic eruptions, nullify such forecasts

(idw - Leibniz Institute for Marine Sciences, 05.05.2008 - DLO)