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Will the UK have the climate of Madeira by 2060, as Costing the Earth suggests?

  • 17 Aug 2012, 12:38
  • Verity Payne

It might seem like a slightly bizarre comparison to say that Britain could soon have the 'climate of Madeira' - but that's what this week's BBC Radio 4 Costing the Earth argues. It suggests that, due to climate change, the UK's climate could "look and sound something like ... Madeira" by 2060. The programme says it's got this comparison from findings of the Met Office's the UK Climate Projections (UKCP09).

This was obviously an opportunity to visit the island, and who can blame the programme makers for seizing that? But Met Office Head of the Climate Impacts Richard Betts, who worked on UKCP09, calls the premise of the programme "inaccurate information". The UK is unlikely to be as hot as the Portuguese archipelago by the 2060s, he says.

UK's Mediterranean climate future?

In a Radio Times article accompanying the programme, presenter Tom Heap writes that according to Dr Peter Carey of the company Bodsey Ecology Limited:

"[B]y 2060 Britain could have the climate Madeira enjoys today [...] much of the country could be 3-6 [ºC] hotter, but rainfall the same or higher."

Carey reached this conclusion, explains Heap, after "careful scrutiny" of the UKCP09 as part of research for adaptation project the Living with Environmental Change Programme. We assume that this research will be contained in a currently-unpublished background paper Carey is submitting to the government's Terrestrial Biodiversity Climate Change impact report card.

Carey tells Heap at the start of the programme:

"It looks like the southwest of England, Wales, northern England, Scotland are going to become a lot warmer, so maybe 5-7 degrees [Celsius] warmer than they are now, but also wetter, or as wet, and that will mitigate the effects of the temperature. In fact the climate will become quite like the Azores or Madeira... so it could be a very interesting place to be"

Richard Betts, contributing author to the UKCP09 scientific reports, disagrees. He criticises the show via Twitter, writing:

"Inaccurate information from @BBCRadio4 . UKCP09 climate projections do NOT say UK climate will be like Madeira in 2060"

Betts explains:

"For UK temperature to be 'like Madeira in 2060' would need very rapid warming. Also rainfall regime is very different."

Temperature

Betts tweets that the UKCP09 report projects an upper limit for warming of around 6 degrees Celsius (ºC) by the 2080s - 20 years later than Costing the Earth's suggested date, in a future where greenhouse gas emissions are high.

We looked in more detail. UKCP09 is based on climate modelling that describes the change in temperature compared to a baseline of UK temperatures averaged over 1961-1990, and gives different warming for summer and winter. The projections are informed by IPCC greenhouse gas emissions scenarios. The 'high' scenario which we looked at is based on the IPCC's A1F1 scenario.

The image below, from the UKCP09 report, shows temperature projections for the high emissions scenario. The third column of maps gives the UCKP09 central estimate for summer and winter in the 2080s.

UKCP09 2080 mean T projections

Maps showing projections of temperature rise by the 2080s for summer and winter based on the high emissions scenario. Column 1: temperature rise from UK climate projections 2002 (UKCP02); column 3: UKCP09 central estimate for temperature rise; temperature rise very unlikely to be less than column 2 or more than column 4. Source: UKCP09 climate change projections report.

During summer, the UKCP09 central estimate of warming for a high emissions scenario is 4 to 5 ºC. Warming of less than 2 degrees or warming of more than 7 to 8 ºC are both considered very unlikely.

The average UK summer temperature measured between 1961-1990 ranges from around 10 ºC to about 17 ºC (see the map below), so from by our rough calculations this would give a range for UK summer temperatures in 2080 (rather than 2060) of about 15 to 22 ºC - nearly comparable to Madeira's summer temperature range of roughly 19 - 23 ºC.

MO summer 6091 temp

Map showing average summer temperature across the UK between 1961 and 1990. Source: UK Met Office.

In the winter, the UKCP09 central estimate of warming for a high emissions scenario is 3 to 4 ºC. Warming of less than 1 to 2 ºC or more than 5 to 6 ºC is considered very unlikely.

The average UK winter temperature measured between 1961-1990 ranges from below freezing to over 6 ºC (see the map below). So from our rough calculations UKCP09 puts UK winter temperatures in 2080 between 3 and 10 ºC - quite a bit colder than the relatively balmy 15 - 17 ºC of Madeira's capital Funchal during the winter months.

MO winter 6091 temp

Map showing average winter temperature across the UK between 1961 and 1990. Source: UK Met Office.

To sum up; assuming a high greenhouse gas emissions scenario, UKCP09 says that by the 2080s we could see temperatures in some parts of the country which are kind-of-comparable with current summer temperatures in Madeira. But in winter, even by the 2080s, the UK is still projected to be markedly cooler. And this is twenty years later than the date Costing the Earth was talking about.

What about precipitation?

What about the suggestion that rainfall will be "the same or higher"?

The image below is from the UKCP09 report, and shows precipitation projections for the high emissions scenario.

The column to look at is the third one, which gives the UKCP09 central estimate. It shows (roughly) that in winter the UK is projected to be mostly 15-30% wetter, and in summer mostly 15-30% drier. However, it's worth pointing out that projections for how much precipitation the UK will receive vary pretty widely - reflected by the range of estimates in the second and fourth columns.

UKCP09 2080 mean precip projections

Maps showing projections of precipitation change by the 2080s for summer and winter based on the high emissions scenario. Column 1: preciptation change from UK climate projections 2002 (UKCP02); column 3: UKCP09 central estimate for precipitation change; precipitation change very unlikely to be less than column 2 or more than column 4. Source: UKCP09  climate change projections report.

Carey may have other climate modelling to support his suggestion that UK's climate could be similar to Madeira's by 2060, but based on UKCP09 it doesn't quite fit.

Comparing future UK climate scenarios with other countries' current climates seems like a valuable exercise, since trying to picture how the temperature anomalies projected by climate models might look in reality is challenging.

We're not sure, however, how accurate or useful suggesting the UK's reasonably sizable islands, which have a fairly complicated local climate, could have a climate 'like Madeira' - a small, mountainous archipelago in the Atlantic. Even if precipitation and temperature were about the same in the Madeira of today and the UK of the future, there might well be other important differences.

Betts suggests that despite "2060 being far too early for such warming," Costing the Earth is "an OK attempt to illustrate what warming means [for the] UK". It certainly gives an indication of both the potential benefits and risks of that level of warming to the UK, although the primary thing we've taken away from the program is the desire to go to Madeira on holiday.

Update 14:10 17/08/12: 

Met Office climate impacts research scientist Mark McCarthy tells us in an email: 

"To say the present-day climate of Madeira may equate to a possible future climate of the UK in the 2060s is impossible.

The subtropical latitude of Madeira means the fundamental nature of both the weather and climate is markedly different from the UK which not only sits in temperate latitudes, [but] also has the European continental land-mass for a close neighbour.

Significant changes to the UK climate are expected as a consequence of global climate change by the 2080s, but even the biggest projected changes under the highest emissions scenarios do not provide evidence that this would resemble today's climate of Madeira, and certainly not by the 2060s."


Update
 15:15 20/08/12: 

Dr Peter Carey tells us in a comment below this blog that no country's climate gives a perfect example of what climate models project for the UK, this is why he suggested the UK's climate might be "a bit like" Madeira's by 2060.

He explains that he has been using the UKCP09's Spatially Coherent Projections - an ensemble of 11 climate models that can project changes to climate at a 25 kilometre resolution - to work out how local vegetation might change with climate. But, he points out;

"[T]he range of increase in temperature is very varied for each place and between places. It is extremely difficcult to say anything certain when there is such variation in the climate models and also with the very complicated population dynamics involved in the death of one species and its replacement by one or more others. it is an incredibly inexact process and all we can hope to do is give some idea of what might happen."

Carey also suggests that he ought to have said that the UK could face warming of "3 to 6 [ºC] not 5 or 6 degrees [ºC]", and apologises to climate modellers for the error. He explains:

"[T]he Spatially Coherent Projections give higher increases than 6 [ºC] for some areas  and less for others - it is hideously complicated to explain in a few sentences. Does this mean we should not try to summarise?

I totally stand by my assertion that the most likely species to replace those that die (for whatever reason) will be those that will escape from gardens. Citrus, olives, bananas, apricots, peaches will become a lot easier to grow without doubt in England, and I think are unlikely to be limited by light levels in England (I agree Scotland could be an issue here)."

Carey points out that portraying the potential impacts of climate change is important, and highlights his closing message on Costing the Earth:

"[T]he UK is in a lucky position. [T]he impacts of climate change are going to be horrendous worldwide and this will have a much more serious impact on our lives than the climate of the UK"

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