It’s going to rain in Dakar on Tuesday 20 May 2070. How do I know? Michael Saunby told me, at his presentation of Climate Change Mashups this afternoon in the Lebanon Room. But why do we need to know today whether or not it’s going to rain in Dakar on 20 May 2070? “It might not,” confesses Michael, “it’s not a prediction, it’s more like an average of the weather at that time, as far as the computer models can tell.”

Michael works at the Met Office Hadley Centre in the UK. Massively powerful computers there are used to work out how the Earth’s climate might change over the next decades and into the 22nd century. His example of the weather over West Africa on 20 May 2070 illustrates the kind of data being produced. When examined over longer periods this kind of information could indicate particularly high rainfall for the region - invaluable knowledge for people living in coastal regions or along rivers that could flood. Similarly, knowing in advance that sustained periods of drought were likely is crucial to farmers when planning which crops to plant, when to harvest or when developing future irrigation schemes.

But how could a farmer in rural Senegal access information produced by a super computer in the UK? Mashup, is Michael’s answer. Combining Met Office weather data with Google maps, for example, could indicate the likely impact of the changing climate for a specific area and help farmers plan how they can best use the land in the years to come.

This means those most affected could work together with their wider community and even government when decisions are made, taking action early rather than waiting until disaster hits. And disaster will hit. Most experts agree that some aspects of climate change are inevitable – seal levels will rise, the planet will get warmer – and so, while measures can still be taken to prevent or limit damage it is important that the most vulnerable people have the information to contribute to future decision making. Not only that, but web 2.0 now also makes it possible for people to add local information to the data provided by the Met Office and help Michael and his colleagues to make ever more accurate models for future changes to our climate.

Michael’s obvious enthusiasm for the subject made for a lively presentation that not only looked impressive but was incredibly informative too. Just remember, make sure you pack an umbrella if you’re visiting Dakar in May 2070.

Blogs, wikis, podcasts, social bookmarks, and the like are all great ways of collaborating, allowing all Internet users to create new Internet content. Mashups go further, they liberate web users from the role of consumers of Internet services and allow them to create new services and share them.

So what is a mashup? The Wikipedia entry describes a mashup as a web application that combines data from more than one source into an integrated experience.

So what can be created in this way? The directory of mashups at ProgrammableWeb has over 2000 entries. Take a look, you’re bound to find something that interests you.

Or how about creating your own? I’ve put together a simple example at http://wemapr.blogspot.com The starting point is a standard Blogger blog, but to this I’ve added, Yahoo Pipes and Google Maps to give the option of a map based view of the blog entries, click on ‘See this blog as a map’ on the right hand column. On the blog I describe how to add this mapping feature to your own blog. (It’s not perfect, you’ll have to zoom out to see the markers).

Perhaps you’ve created your own mashup, or know of an interesting development related mashup. Please post a comment and share.