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Today the latest state-of-the-art climate models include as many physical, biological and chemical processes as possible. The models are based on mathematical equations that describe the behaviour of the atmosphere and ocean, and their complex interactions with other components of the Earth system, such as the land surface, the biosphere (animals, plants and microbacterias) and the cryosphere (ice mass, such as glaciers and ice sheets). Their core goal is to describe how certain variables in the coupled atmosphere-ocean system, such as temperature, air pressure, winds or ocean currents, have changed in the past and will most likely change in the future. But the climate system is very complex and understanding or predicting climate changes in the future is a very difficult thing to do. And with weather forecasts becoming inaccurate after just a few days, one can easily ask how we can even claim to project most likely weather conditions in the future?

The problem with predicting the weather for the next few days is that there are so many causes which affect our weather, that make it almost impossible to forecast what our weather is going to do next. In the long term however, climate models are able to deal with the climate system’s chaotic behaviour. That means that even though climate researchers cannot predict the weather for individual days, they can give suggestions about what the average weather conditions for a certain region would look like in the future, including the probability and magnitudes of deviations from this average.
However, it is important to understand that even though climate models are continually evaluated against datasets of real observations, they are still just mathematical approximations of the climate system and no real systems themselves. Therefore their results always have to be treated with scientific caution.

Extreme weather events associated with a changing climate?

Since the late 1970s we have been seeing a significant increase in climate related extreme weather events. But it was not until just a few years ago, especially with the occurrence of the record-breaking hurricane season of 2005 including Katrina, the first ever hurricane in the South Atlantic in 2004, and the 2003 heat wave in Europe, that the public started to raise the question, whether this increase might possibly be associated with the changing climate. Even though the chaotic behaviour of the weather makes it yet impossible to prove that a single event could have been caused by global warming, the latest increase of extreme weather events may indicate some contribution from the changing climate we are already observing.

What can we expect in the future?

A growing body of evidence indicates that the Earth is warming and that this warming has been caused primarily by human activities that have increased the concentration of greenhouse gases in the atmosphere in recent decades. Although the question how the climate will change in the future, due to anthropogenic forcing, still cannot be answered with great certainty, it is far from unknown.
The anthropogenic impact on the climate can be best described by using the picture of a loaded dice. The situation of a human induced Climate Change is very analogous to a human-altered set of dices where the sixes occur twice as often as normal. The “loading” of the climate system comes from the increase of greenhouse gases, such as the carbon dioxide, and rises the Earth’s temperature. This leads to an increased probability of extreme weather events in the future. Just like the loaded dices would lead to an increased occurrence of sixes with every next roll. Due to the still random nature of the dices, however, we won’t be able to tell when the next six will occur. Extreme weather events behave in a very similar manner: even though we can calculate their statistical frequency, for example that they will increase in the future due to higher temperatures, we still do not know when exactly they will occur. This also explains why climate predictions are possible in the long term, although weather forecasts are generally limited to short time periods. Furthermore the picture of the loaded dices also emphasizes the fact that even though a certain occurrence has been observed before, it doesn’t tell you much about the dices quality or whether or not they have been manipulated in the first place: half of the sixes would have occurred anyway, even with two normal dices. But loading the dices has doubled the odds. Transferred to the climate system this means that the human induced increase of the global temperatures has increased the odds and has made the occurrence of extreme weather events more probable. As you would have thought this is exactly what has been observed since the 1970s when the anthropogenic forcing really began to change the climate system. Extreme weather events such as hurricanes, droughts, heatwaves have increased in their frequency as well as in their magnitude over the last decades. It is that “anomalous” number of unusual weather patterns that is meant by the definition of “Climate Change” and is once again highlighted by the unusual warm meteorological Northern Hemisphere winter we are currently seeing.
And with 2007 most likely to be the warmest year on record globally, partly arising from a moderate-strong El Nino as well as from the still increasing greenhouse gas emissions, the Earth’s future gets bleaker with every day we don’t stop gambling with it.

But there still is time to avoid dangerous human-made interferences with the climate system. And as long as there is time, there is hope for the Earth’s future too. The power of this hope lies in the present though. And if we don’t start changing our energy wasting way of living, if we don’t start reducing our greenhouse gas emissions drastically, we will soon notice that we have closed the window of opportunity and have pushed the Earth into a “fever hysteresis” from it won’t be able to recover for millennia.
In order to save a planet that will be inherited by our children and grandchildren urgent action is needed. Action that involves everyone, everywhere – now!