Monday, November 29, 2010

Cold UK weather does not disprove Man-Made Global Warming

Just as the Daily Telegraph letters page reliably has an April entry from someone who has heard the first cuckoo of Spring, so also we should shortly expect letters happily claiming that the current cold weather disproves man-made global warming.

The fact is that despite the abnormally cold weather in parts of the Northern Hemisphere last winter (and now), global data suggests that 2010 is likely to be warmer than 1998, the previous record. Obviously, the full data is not yet in, and a volcano (causing cooling) could cause 2010 to lose out.

The current cold weather in the UK is balanced by abnormal warmth in North America.

[thanks to the Met Office for the graph]

We see a band of abnormal cold blue across Northern Europe and Russia, with warm reds counterbalancing it in other areas.

The Met Office does not mention the Northern Polar Jet Stream, but it is well south of its normal position, north of Scotland. In fact, it is today shooting across the Bay of Biscay. This downward displacement may be due to low solar activity in the last few years, because higher solar activity (and long term global warming) tends to push the jet stream northwards.

Here's the current position of the jet stream.
It is winding down eastwards north of Scotland (easterly jet streams are a bit unusual) then looping back over France.  The blues and yellows denote the jet stream.

So that's why it is cold.

Which illustrates the distinction between weather and global climate. Weather is what is experienced in any specified part of the planet. Global climate is the sum total of temperatures measured all over the planet.

Take a look here at what happened last year: abnormal cold in normally temperate areas, and abnormal warmth in normally cold areas.


Unknown said...

How ridiculous. We are the coldest we've been in 40 years throughout the Norther hemisphere, yet we're going to have the warmest average year since records began, or something. How does that work? What kind of GLOBAL warming makes one part of the world very hot and another very cold? Much of the figures are adjusted and estimated anyway.

Please explain how winters are GETTING COLDER at the same time that CO2 is making things WARMER.

weggis said...

Have you never had a "temperature" and felt "cold"?

DocRichard said...

Hello Simon.

Thank you for commenting, and asking "How does that work?".

Let me explain with a simple example.

Say there are 3 boys, Tom, Dick and Harry who each have 3 apples a day to give to teacher.

Each day the teacher gets 9 apples (3x3=9)

But one day one of Tom's apples falls out of his bag and into the river.

By coincidence, Dick and Harry are given 4 apples each that day to give to teacher, because their mothers are fed up with making stewed apples.

So Dick and Harry give the teacher 8 apples (2x4=8) and Tom gives her 2 apples, so instead of getting 9 apples, teacher gets 10 apples, despite Tom's apple deficit.

I hope that helps. If there is anything you still find difficult, please ask again.

This story is an allegory. Tom, Dick and Harry are three different parts of the world, the apples are local temperatures, and the Teacher is the whole world.

Thanks for asking.


DocRichard said...

Thank you for your ever-helpful contributions...