Should climate models have predicted the pause?

27 09 2013

Media coverage today of the launch of the 5th Assessment Report of the IPCC has again said that global warming is “unequivocal” and that the pause in warming over the past 15 years is too short to reflect long-term trends.

Over recent days some commentators have criticised climate models for not predicting the pause. It’s good to see this being addressed, and so begin to clarify the difference between climate model projections and predictions.

We should not confuse climate prediction with climate change projection. Climate prediction is about saying what the state of the climate will be in the next few years, and it depends absolutely on knowing what the state of the climate is today. And that requires a vast number of high quality observations, of the atmosphere and especially of the ocean.

Whilst the last decade has seen a rapid increase in good observations of the surface and upper ocean, thanks to Argo floats, we have very few for the deep ocean. Without these requisite observations to initialise, i.e. set running, a climate prediction, it is impossible to have predicted the current pause, however good the climate models.

On the other hand, climate change projections are concerned with the long view; the impact of the large and powerful influences on our climate, such as greenhouse gases. Projections capture the role of these overwhelming influences on climate and its variability, rather than predict the current state of the variability itself.

The IPCC model simulations are projections and not predictions; in other words the models do not start from the state of the climate system today or even 10 years ago. There is no mileage in a story about models being ‘flawed’ because they did not predict the pause; it’s merely a misunderstanding of the science and the difference between a prediction and a projection.

As the IPCC states in line with our three papers on the pause, the deep ocean is likely a key player in the current pause, effectively ‘hiding’ heat from the surface. Climate model projections simulate such pauses, a few every hundred years lasting a decade or more; and they replicate the influence of the modes of natural climate variability, like the Pacific Decadal Oscillation (PDO) that we think is at the centre of the current pause.

The Daily Telegraph today also covers the science of the pause.

Critically there is ever more confidence that the world is warming as a result of human actions, and limiting climate change would require substantial and sustained reductions in emissions of carbon dioxide (CO2) and other greenhouse gases.





Met Office in the Mail on Sunday

15 09 2013

An article appears in the Mail on Sunday today focusing on the Intergovernmental Panel on Climate Change’s (IPCC) forthcoming Fifth Assessment Report (AR5) which it bills this as the ‘world’s most authoritative climate study’.

It’s fair to say that AR5 is expected to be the most comprehensive review of climate change science to date. The first part of the report, from its Working Group I (WGI), has been worked on by more than 800 scientists from around the world who have assessed more than 9,000 scientific publications and taken into account more than 50,000 comments from over 1000 expert reviewers.

The WGI report is now in its final stages and the major conclusions will be finalised and released on 27 September. It is at that point that we should debate its findings and their implications.

Further parts of the report, from its Working Group II and III, as well as a final version of the whole report will be published next year.

The Mail article also discusses the recent pause in warming, which the Met Office looked at in a series of papers, released in July. Many of the issues raised in the article are addressed in those reports, which you can see on our website.

The article also goes on to mention some of the claims made in a commentary published by Nic Lewis yesterday. This is a lengthy and technical commentary covering several topics and will require time to provide as helpful a response as possible, so further comment will be released in due course.

There are a couple of points raised in the Mail story which should be addressed now, however.

The article states that the Met Office’s ‘flagship’ model (referring to our Earth System Model known as HadGEM2-ES) is too sensitive to greenhouse gases and therefore overestimates the possible temperature changes we may see by 2100.

There is no scientific evidence to support this claim. It is indeed the case that HadGEM2-ES is among the most sensitive models used by the IPCC (something the Met Office itself has discussed in a science paper published early this year), but it lies within the accepted range of climate sensitivity highlighted by the IPCC.

Equally when HadGEM2-ES is evaluated against many aspects of the observed climate, including those that are critical for determining the climate sensitivity, it has proved to be amongst the most skilful models in the world.

Finally, in our aim to provide the best possible scientific advice to the UK Government, the Met Office draws on all the scientific evidence available to us. This includes many other physically based climate models from leading research centres around the world, which provide a range of climate sensitivities and a range of potential future warming.





August Bank Holiday weather extremes

23 08 2013

The August Bank Holiday is always the last Monday in August, although these statistics include Saturday and Sunday, to look at the whole weekend. At this time of year it can still be quite hot, although there have been few instances of this actually being the case over the Bank Holiday weekend itself. In some years the progression of Atlantic low-pressure systems have arrived by the end of August, bringing wind and rain.

Here are the warmest, coldest, wettest and windiest August Bank Holiday weekends, as provided by the Met Office National Climate Information Centre.

Warmest

Temperatures reached 31.6 °C at London Weather Centre on Saturday 25 August 2001, and more than twenty stations exceeded 30 °C on that day, mostly in the south-east and East Anglia. Saturday 25th August 1990 was also very warm in many parts.

Coldest

Numerous Scottish stations failed to get above 10 °C on Sunday 28th August 2011, the lowest maximum being 9.1 °C at Cromdale. This excludes stations 500 metres above sea level, which may be considerably colder.

There have also been numerous instances of air frost over the August Bank Holiday, most of them in Scotland, most notably in 1977 and 1982. The lowest individual reading was -3.1 °C at Kindrogan on Sunday 28 August 1977.

Wettest

On occasions 100 mm or more of rainfall has been recorded in a day. The highest 0900 GMT – 0900 GMT figure is 152.2 mm, recorded at Glendessary on Monday 31 August 1992. Widespread heavy rainfall also came from the remnants of Hurricane Charlie on Monday 25 August 1986.

Windiest

A maximum gust of 78 mph was reported at Lerwick on Monday 29 August 2005. Strong winds were also relatively widespread in 1986 and 1992.

Check your local Bank Holiday weather forecast on our website.





Weather on the 27 July

27 07 2013

Today marks a year since the opening ceremony of the Olympic Games, so to celebrate a year since the Games, we’ve taken a look back at the weather on 27 July.

The Met Office holds the UK’s weather and climate records, and we’ve created this infographic with daily weather statistics from the last 5o years.

Weather on the 27 July

View larger version (PDF).

Find out what weather is in store this year at London Anniversary Games on our website.





A response on statistical models and global temperature

31 05 2013

Over a period of several months the Met Office has been involved in dialogue and answered a series of questions on the subject of the use of statistical models in relation to the global temperature record.

The Met Office’s Chief Scientist, Julia Slingo, has written a discussion paper on the subject – you can now view the Executive Summary and a link to the full paper in an article on our Research News pages.

Publication of this paper follows a guest article recently published on the Bishop Hill blog site, where one of the people with which the Met Office has been speaking with – Doug Keenan – makes a series of accusations about the Met Office and its science.

Professor Slingo’s paper answers many of the points Mr Keenan makes, and the Met Office has already directly addressed many of the points Mr Keenan raises through considerable previous correspondence we have had with him on this issue. However, here we directly address a few of the key points in Mr Keenan’s article:

1)       Mr Keenan says that there is “no basis” for the claim that the increase in global temperatures since the late 1800s is too large to be reasonably attributed to natural random variation. He goes on to argue that this is because we haven’t used the right statistical model.

However, the claim that the increase in global warming is larger than could be explained by natural variability has a clear and well understood grounding in fundamental physics and chemistry. There is very high confidence (using the IPCC’s definition) that the global average net effect of human activities since 1850 has been one of warming. The basis for this claim is not, and never has been, the sole use of statistical models to emulate a global temperature trend. Instead it is based on hundreds of years of scientific advancement, supported by the development of high-quality observations and computational modeling.

2)       Mr Keenan suggests that Met Office scientists have been ‘trying to cover it [point 1, above] up’.

The Met Office has entered into email discussion at the working scientific level and responded promptly and transparently on all parliamentary matters and questions. We have also responded to numerous emails from Mr Keenan and invited him to come to the Met Office to discuss statistical modeling in climate science. As he points out in his article, so far those invitations have been declined or unanswered. The invitation still stands.

3)       Mr Keenan then goes on to argue that you can only use a statistical model to determine whether the warming we have seen is statistically significant. He argues that the Met Office has used the wrong statistical model and, therefore, our science is flawed.

The study of climate variability and change is broader than the domain of statistics, most notably due to the importance of the underpinning science of the climate system. Our judgment that changes in temperature since 1850 are driven by human activity is based on information not just from the global temperature trend, or statistics, but also our knowledge of the way that the climate system works, how it responds to global fossil fuel emissions and observations of a wide range of other indicators, such as sea ice, glacier mass, sea level rise, etc.

Using statistical tests in the absence of this other information is inappropriate, particularly when it is not possible to know, definitively, which is the most appropriate statistical model to use. In particular, a key test of an appropriate statistical model is that it agrees with everything we know about the system. Neither of the models discussed by Mr Keenan is adequate in this regard. On that basis, this conversation on statistical modelling is of little scientific merit.

4)       Mr Keenan details his argument to say that various different statistical models can emulate the global temperature record better and worse than others.

This is something the Met Office has already spoken about and shown analysis on (such as in an answer to a parliamentary question (PQHL62)). However, this assessment of relative likelihood does not ensure that any of the statistical models are scientifically valid. Because the Met Office does not make an assessment of global warming solely on statistics – let alone the statistical models referred to in Mr Keenan’s article, this exercise is of very little, if any, scientific use.

5)       Mr Keenan also makes repeated accusations that the Met Office did not, or was not willing to respond to Parliamentary Questions.

This is not the case. The Met Office answered every request for input to Parliamentary Questions and answered them in the most scientifically appropriate way to the best of its knowledge. There has never been a refusal to provide information to answer a Parliamentary Question.





Spring on track to be coldest for 30 years

22 05 2013

Early figures from the Met Office show spring (March, April and May) 2013 is on course to be the coldest in the UK since 1979.

Estimates of the mean temperature for the whole season have been made based on data from 1 March up to 15 May as well as an assumption of average conditions through to the end of this month. The final figures could therefore be different, depending on the temperatures we actually see up to the end of May.

The estimates suggest the mean UK temperature for spring will be around 6.1 °C, which would make it the 6th coldest spring in national records dating back to 1910 and the coldest since 1979 when the mean temperature was 6.0 °C.

The estimated figure this year goes against recent form for spring, with eight of the past ten years being above the long-term (1981-2010) average for the season of 7.7 °C.

However, looking further back, the most recent colder spring of 1979 came in the middle of a long run, lasting from 1962 to 1989, of springs which were almost all colder than the current average*.

This year’s particularly cold spring was heavily influenced by an exceptionally cold March which had a mean temperature 3.3 °C below the long-term average. April and May (so far) have been less cold, but have also registered slightly below average mean temperatures.

The colder than average conditions have been caused by frequent east and northerly winds which have brought cold air to the UK from polar and northern European regions.

This spring also looks to be slightly drier than average, with an estimate of about 214 mm of rain which would be roughly 90% of the average amount we would expect through the season. This isn’t that notable when compared with the the springs of 2010 and 2011, which were much drier – notching up 79% and 70% of the average respectively.

Estimated provisional statistics for spring 2013

UK England Wales Scotland NI
Mean temp (° C) 6.1 6.8 6.2 4.7 6.3
Diff from avg (° C) -1.7 -1.7 -1.8 -1.6 -1.5
Coldest since: 1979 1962 1979 1979 1986
Rainfall (mm) 214 158 246 292 240
% of avg 89.8 87.3 84.3 92.3 99

*The Met Office operates 30-year climate averages which are updated every decade. Looking at the 30-year averages of 1961-90, 1971-2000 and the current climate averages of 1981-2010, you can see the average mean temperatures for spring have increased over that period. This means defining what is ‘below-average’ depends on which 30-year period is used. All references in this article use the current 1981-2010 climate averages.

30-year period                 Average spring UK mean temperature

1961-1990                                            7.1 °C

1971-2000                                            7.4 °C

1981-2010                                            7.7 °C





Recent climate research in the news

21 05 2013

A research paper published in Nature Geoscience (Otto et al, 2013) led to a fair amount of media coverage yesterday, including articles in the Guardian, BBC and an opinion piece by Matt Ridley in The Times (this article is behind a pay wall).

The research paper looked at a ‘best estimate’ of the warming expected when the concentration of carbon in the atmosphere is doubled over pre-industrial levels (known as the Transient Climate Response).

Alexander Otto, Research Fellow in Climate Decisions at the Environmental Change Institute, University of Oxford, was the lead author of the research.

He has written an article discussing the science and the implications of the research which can be seen on the Research News pages on our website.

Here is a short extract from Alexander Otto’s article :

“We published a paper in Nature Geoscience on Sunday giving a new best-estimate of 1.3°C for the Transient Climate Response, or the warming expected at the time carbon dioxide reaches double its pre-industrial concentration, using data from the most recent climate observations.

This best-estimate is lower than the HadGEM2 [one of the Met Office climate models] TCR value of 2.5°C and it is also 30% lower than the multi-model average of 1.8°C of the CMIP5 models used in the current IPCC assessment. Does this mean that the Met Office’s advice to government is based on a flawed model? Certainly not.

It is well acknowledged by all that the HadGEM2 model is at the top end of the range of TCR values in CMIP5, but we need a diverse range of TCR values to represent the uncertainties in our understanding of climate system processes. And the Met Office’s advice to government, like any solid policy advice, is based on the range of results from different models, not just their own.

The ‘warming pause’ over the recent decade does not show that climate change is not happening. And it certainly does not mean that climate scientists are “backing away” from our fundamental understanding.

Every new decade of data brings new information that helps reduce uncertainties in climate forecasts. In some ways, the picture changes surprisingly slowly for such an intensely scrutinised problem… This study highlights the importance of continued careful monitoring of the climate system, and also the dangers of over-interpreting any single decade’s worth of data.”





March is joint second coldest on record

2 04 2013

Provisional full-month Met Office figures for March confirm it has been an exceptionally cold month, with a UK mean temperature of 2.2 °C.

This is 3.3 °C below the 1981-2010 long-term average for the month, and ranks this March as joint second coldest (with 1947) in our records dating back to 1910. Only March 1962 was colder, with a record-breaking month mean temperature of 1.9 °C.

In an unusual turn of events, this March was also colder than the preceding winter months of December (3.8 °C), January (3.3 °C) and February (2.8 °C). This last happened in 1975.

Looking at individual countries, the mean temperature for England for March was 2.6 °C – making it the second coldest on record, with only 1962 being colder (2.3 °C). In Wales, the mean temperature was 2.4 °C which also ranks it as the second coldest recorded – with only 1962 registering a lower temperature (2.1 °C). Scotland saw a mean temperature of 1.3 °C, which is joint fifth alongside 1916 and 1958. The coldest March on record for Scotland was set in 1947 (0.2 °C). For Northern Ireland, this March saw a mean temperature of 2.8 °C, which is joint second alongside 1919, 1937, and 1962. The record was set in 1947 (2.5 °C).

This March was also much drier than average for the UK, with 62.1mm of rain falling during the month – just 65% of the 95.1mm average. Scotland was particularly dry, seeing 49.5mm of rain which is 35% of its long term average for the month.

Sunshine hours were also slightly down compared to average, with 82.9 hours for the UK notching up 81% of the average.

The cold and dry conditions seen in March were largely due to high pressure dominating UK weather patterns, allowing cold and relatively dry air to move in from the east. While this pattern is set to continue through the first week of April, milder and more unsettled conditions are expected to move in for the start of next week. You can stay up to date with the latest information with the Met Office’s forecasts.

March 2013 Actual Difference from average Actual % of average
Regions °C °C mm  %
UK 2.2 -3.3 62.1 65
England 2.6 -3.6 64.4 101
Wales 2.4 -3.4 86.2 74
Scotland 1.3 -2.9 49.5 35
N Ireland 2.8 -3.1 74.1 78
England & Wales 2.6 -3.6 67.4 95
England N 1.8 -3.7 56.4 75
England S 3 -3.5 68.6 118

March – top five coldest in the UK

1 1962 1.9 °C
2 2013 2.2 °C
2 1947 2.2 °C
4 1937 2.4 °C
5 1916 2.5 °C




Fascination and forecasting – guest blog by Siân Lloyd

5 03 2013
Siân Lloyd

Siân Lloyd

Here in the UK we’re famous for being obsessed with the weather, and I’m no exception to that. My fascination with the weather started from a young age because my father had a passion for the outdoors, so we were always out in all weathers.

Coming from Wales, where we get continually walloped by fronts spinning off the Atlantic, you certainly see a great variety of weather and you soon get used to coping with whatever gets thrown at you. I remember eating egg and marmite sandwiches on Gower beaches, sat in a kagool with my father saying the rain would clear soon – he was always an optimist.

It’s not just my own experiences that captured my fascination, but also the myths and legends of the Celtic landscape I grew up in. Virtually every story has weather in it – from violent storms, to great floods, or the tranquil calm of a summer’s day. So for me, weather represents the drama of life and is the very stuff of our literature.

So it doesn’t surprise me that, wherever I go, people are always keen to talk about the weather and what’s in the forecast. I know I may be biased, but I really do believe that forecasting is hugely important. From protecting people from the harshest conditions our climate has to offer, to helping fashion conscious ladies like myself decide what to wear, forecasts help us in so many aspects of our day to day lives.

In many ways we take forecasting for granted, but to me the ability to predict the weather days ahead is a true feat of human ingenuity and one of the great triumphs of science. In 1922, mathematician Lewis Fry Richardson estimated you’d need 64,000 people doing endless calculations to get a forecast in time to make it useful – looking just a few hours ahead. Today we take observations from all over the world, from the top of the atmosphere to the depths of the oceans, put them in a supercomputer that does trillions of calculations a second to make forecasts, then people like me interpret that output to put together tailored forecasts which can be transmitted around the world in seconds. Truly amazing stuff.

I’ve been in weather forecasting for 20 years and things have changed a lot. One of the biggest changes is the huge strides in accuracy that have been made. Even from my personal experience I can tell how much better forecasts are and the statistics bear that out. The Met Office’s four-day forecasts are as accurate as its one day forecasts were 30 years ago, and things are still improving all the time as we understand more about the way the atmosphere works and technology improves.

The other big thing that I’ve noticed is that the weather used to follow the news, but now it very often is the news. So often these days I get asked to speak on air during bulletins about floods or droughts and why we’re seeing them. So, from my personal experience, it seems like the weather is changing and that our warming climate is playing a part. As we go forward then, science once again will have an important role to play in helping us understand how and why things are changing, and ever more accurate forecasting will help keep everyone prepared for whatever the weather has in store.

If you want to learn more about our weather and climate, as well as how it all works, you can read about it in ‘An Essential Guide to the Weather’ – a two part guide which will be free in The Telegraph this weekend on the 9th and 10th of March. Part 1, in Saturday’s paper, explains the causes of our weather and provides a comprehensive guide to clouds and other types of weather. Part 2 looks at how weather forecasting is done, extreme weather, and climate zones around the world.





Top ten: Mildest temperatures recorded last night

23 10 2012

Yesterday was a mild day with temperatures reaching as high as 19.2 °C, which was recorded in Langdon Bay during the daytime. However night-time temperatures were also mild for the time of year, with many areas not dropping below 10 °C. Jersey was particularly warm, not falling below 13.5 °C last night.

Station Temperature (°C)
Jersey: Airport 13.5
Bognor Regis 12.9
Guernsey: Airport 12.9
Langdon Bay 12.1
Manston 12.1
Frittenden 11.9
Herstmonceux, West End 11.9
Faversham 11.8
Scilly: St Marys Airport 11.7
Skegness 11.7

Overnight lows at this time of year would typically be around 7 to 9 °C across southern England, making last night around 4 or 5 °C milder than average. More UK climate and weather statistics are available on our website.








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