Planet Earth Online

Explaining climate extremes

21 September 2012

Extreme events like hurricanes, floods and drought seem to be hitting the headlines all the time. Scientists are often asked whether human influence on the Earth's climate system is behind these events, and whether it will affect the frequency or intensity of climate extremes in the future.

This question isn't just doing the rounds in the media - it's widely debated among climate researchers too. We know our climate varies with human-induced changes but the problem is it also varies naturally.

We have to use complex computer models to work out whether the changes we can see are larger than we would expect from natural variability, and to make predictions about the future state of the climate (see pp18-19). We have to validate our models with long-term observations which are often taken several times a day from a land and ocean observing network around the world.

Making this happen requires logistical preparation and coordination on an international scale. And communicating the results in a way that makes sense to non-scientists around the world is another skill entirely.

Drawing together climate research from around the world, the Climate Variability and Predictability (CLIVAR) project is coordinating activities that will provide relevant scientific results that people can use to help them adapt to and mitigate the effects of climate change. CLIVAR's international project office (ICPO) has been hosted by the National Oceanography Centre in Southampton for the past 13 years.

This coordination work is crucial because understanding and predicting future extreme climatic events isn't just a scientific pursuit; it's an important economic, environmental and social investment for the whole planet. It's easy to understand why when you look at the damage caused by recent extreme events.

The heatwave that swept across Europe in 2003 claimed over 30,000 lives, reportedly the highest death toll from a natural hazard in 50 years. And diverse effects were felt further afield: the agricultural sector suffered as the drought affected the quality and quantity of crops as diverse as potatoes, cereals and wine, and even animal fodder. This came hand in hand with an increase in production costs. Meanwhile, forest fires raged throughout several countries on the Continent, and glacial retreat in the Alps accelerated during the event.

The indirect impacts of these events are a big problem too. The energy sector suffered in 2003 because the heatwave caused river levels to drop, forcing nuclear plants to shut down because they didn't have enough water to cool the reactors. The situation was made even worse because the demand for power increased as air conditioning units and extra refrigerators were turned on across the continent.

The UK felt the effects of the 2010 heatwave in Russia, which led indirectly to an increase in the price of our staple goods like pasta and bread. This was because Russia's wheat crops failed, and with less available for export, countries like the UK had to look to China to bolster supplies, which pushed up the price of wheat and wheat-based products.

All this highlights how important it is for policy-makers, and others who rely on accurate climate predictions, to have access to clear information at the right time. In the same way that you and I might rely on the weather forecast to decide whether to have a barbecue or put the washing out, others need climate information to make strategic decisions on slightly longer timescales.

For example, farmers need to know how much rain will come during the following growing season. If drier conditions are predicted, they may decide to invest in irrigation, or plant crops more tolerant to drought conditions. Looking even further ahead, a national health service in a tropical country needs to know when wet and hot weather is coming so they can plan for the increased outbreaks of malaria these conditions typically cause.

Similarly, water companies need to plan ahead to make sure supplies do not run dry. Governments and local authorities need even longer forecasts, so they can use climate information to plan adaptation strategies, from national water-supply strategies to strengthening sea defences against rising sea levels and more intense storms.

The difficulty is in translating the language of graphs, trends and uncertainty into something that can be applied to real-world circumstances, as well as the more traditional language barriers we encounter when providing guidance to international communities. But even more importantly, people have to have access to science information that is relevant to their needs. This is where organisations like CLIVAR are making a difference.

Some key organisations can play a vital role by providing a link in the chain of communication, working with local communities to help interpret scientific information. For example, CLIVAR is working with the UK Met Office, to coordinate the transfer of expertise, including state-of-the-art climate research, so that national meteorological services in developing countries are better equipped to provide information to their own user communities.

These climate services are increasingly the focus for CLIVAR, helping people turn science into action. The international project office in particular is acting as a conduit between scientists and science-users, and building on existing local and regional activities to help people around the world prepare for future climate changes.

Keywords: Atmosphere, Climate system, Environmental change, Weather,

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