14 Jun 2013

Met Office gathering experts to discuss unusual UK weather

On Tuesday, the Met Office is gathering around 20 experts from UK academia to discuss the unusual run of weather that has been experienced in recent seasons and examine some of the potential causes.

The purpose of the meeting is to try and establish whether the unusual weather is simply down to natural variability or linked to the impacts of climate change – something that is ever more important to understand, given how much weather affects us all.

Stephen Belcher, Head of the Met Office Hadley Centre and chair of the workshop, said: “We have seen a run of unusual seasons in the UK and Northern Europe, such as the cold winter of 2010, last year’s wet weather and the cold spring this year.”

He added: “This may be nothing more than a run of natural variability, but there may be other factors impacting our weather.”

One such topic on the agenda is to look at whether declining Arctic sea ice is affecting the climate of Europe, although there are uncertainties about how much weight this factor carries amongst other possible influences.

Natural variability versus climate change

There is no doubt that our climate is changing, but it is important to remember that it always has done during the history of our planet.

However, a key point that is up for discussion is how much human activity has influenced our climate during the last century, during which there has been a marked increase in global temperatures.

The difficulty scientists have is separating out and determining how much of our changing climate is down to natural variability and how much is due to climate change.

This is why it unwise to look at a single extreme weather event and say categorically whether or not climate change is responsible. It is better to look at the bigger picture over time and focus on whether the odds of extreme weather happening have changed.

Declining Arctic sea ice and the jet stream

As I often mention in my blogs, the jet stream – a fast-moving ribbon of air high up in the high up in the atmosphere – is responsible for the weather that we experience at the surface and is influenced by a number of factors.

The jet stream is driven by the contrast in temperature between the cold poles and the warm equator. This sends a ribbon of wind around the earth from west to east at mid-latitudes, travelling at speeds of up to 200mph.

As the level of Arctic sea ice declines, the Arctic warms more readily as less incoming solar radiation from the sun is reflected back into space.

With a warmer Arctic, the temperature contrast between the poles and the equator is lessened, which is thought to weaken the jet stream.

When the jet stream becomes weaker, it tends to meander around more slowly and get stuck in the same place for extended periods of time.

It’s the jet stream getting stuck that increases the risk of extreme weather at a given location, as it gets pounded by the same type of weather for week after week or even month after month – just as we did last summer.

There are other factors that are thought to have an impact, such as sea surface temperatures in our oceans, sudden warming events in upper part of earth’s atmosphere, as well as tropical weather patterns in the Pacific ocean.

Importance of understanding our changing climate

There is no escaping the fact that weather, and especially extreme weather, has a huge impact upon us all. It not only affects how we behave, it also affects landscape of the planet on which we have to live and feed ourselves from.

Only this week, the National Farmers’ Union reported that wheat harvests are likely to be around 30 per cent lower than last year as a result of the extreme weather over winter, making it the second below-average harvest in as many years.

If you amplify this example on a global scale against a growing population, then it highlights even more the importance of understanding what is going on in our atmosphere and how it may impact upon us in the future.

It’ll be interesting to see the outcome of the meeting, which I’ll be keeping a close eye on. You can follow me on Twitter for updates – @liamdutton

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2 reader comments

  1. Philip Edwards says:

    Liam,

    Just a wild conjecture from a layman:

    Do you think the Iceland volcano eruptions of 2010 and 2011 could have something to do with it?

    If the patterns of the last two years become permanent we can forget any notion of “Summer.”

  2. Andrew Dundas says:

    Very useful story of great importance. With issues that are more important than the G9 conference.

    At last! A really important development Conference in understanding and interpreting weather.

    We should note that the Pacific is a vast store of warmth. Warmth that might fuel weather patterns at both poles. Maybe that affects the jet stream too?

    Sea levels are rising faster too. Which, if that continues, could threaten lots of coastal cities.

    Worse than the Taliban threat?

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