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contained in a currently-unpublished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.
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.
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.
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.
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"