Global Warming: Uneven Changes Across Planet | Kate Ravilious

LESS than 2C of global warming for the Earth, the target agreed by leaders at the COP21 climate conference in Paris last November, doesn’t really sound too ambitious. In fact, many of us would welcome an extra couple of degrees warmth. So what is all the fuss about? Unfortunately the warming would not occur evenly around the world. A study published recently in Nature shows what 2C of warming – a rise, of this level, above the pre-industrial global mean surface temperature – might really feel like and which regions may be hit hardest.

Some of the regional hot spots cited are the Mediterranean countries, Brazil and the US, where 2C of global warming could translate into local temperature increases of more than 3C. But the region expected to suffer most is the Arctic, where night-time temperatures are predicted to soar by 6C. “Some countries are much more exposed than others,” says Rob Wilby, from Loughborough University.

The Earth has already warmed by an average of 1C, and the uneven nature of this warming is becoming clear with Arctic regions already beyond the 2C mark. Meanwhile, climate models suggest that the Mediterranean could pass the 2C level once global temperatures have risen by 1.4C. Oceans, which cover 70% of the planet, warm much more slowly than land and are partly responsible for the uneven pattern of warming. Local factors, like loss of heat-reflecting snow in the Arctic, make a difference, too.

And it isn’t just temperature: changes in rainfall are also expected to be unequally distributed, with most land areas getting more of a dousing, according to the researchers. “Recent flooding episodes in the UK give us an insight into just how vulnerable we are,” says Wilby. So far, any impact that climate change may have had generally on regional rainfall cannot be distinguished from natural variations. However, for some specific cases a signal is starting to emerge. A recent study showed that man-made climate change substantially increased the odds of damaging floods occurring in England and Wales in autumn 2000. For the UK, current understanding suggests that increases in heavy rainfall during winter may start to become discernible more generally in the 2020s.

Climate models and observations are improving all the time and the reliability of predictions is likely to improve significantly over the next few years. In particular, new satellites and more detailed models are opening up new possibilities for understanding and predicting how water cycles through the climate system. For example, current climate models typically represent atmospheric processes only down to scales of about 50-100km. This limits their ability to incorporate the effects of mountains and coastlines and means that small-scale processes, such as convection, must be represented by average approximations. In addition, the latest regional climate models capture daily rainfall on large scales but are not good at capturing heavier or more localised events.

Besides global warming is also making the sea saltier, according to new research that demonstrates the massive shifts in natural systems triggered by climate change. Experts at the UK Met Office and Reading University say warmer temperatures over the Atlantic Ocean have significantly increased evaporation and reduced rainfall across a giant stretch of water from Africa to the Carribean in recent years. The change concentrates salt in the water left behind, and is predicted to make southern Europe and the Mediterranean much drier in future. — Courtesy: The Guardian


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