What’s bringing the cold weather to Europe and the UK?

9 02 2012

The current cold weather across Europe is in sharp contrast to the mild, wet and windy conditions across much of Europe through December and January. The cause of the cold conditions is the development of a large ‘blocking’ anticyclone over Scandinavia and north-western Russia. Easterly winds on the southern edge of this system has transported cold continental air westwards, displacing the more usual mild westerly influence from the Atlantic Ocean all the way to the British Isles.

Global land and sea surface temperature anomalies for 1-5 February 2012

Global land and sea surface temperature anomalies for 1-5 February 2012

A ‘blocking anticyclone’ can be thought of being like a very large boulder in a stream. This boulder acts like a dam, stopping the flow of the stream.  In this instance a block stops the more normal westerly flow that brings milder conditions, allowing colder conditions to win out from the east.

The origin and persistence of blocks has been a subject of much research, and unfortunately we are still not absolutely clear on why we see blocks form. What we do know though is that the origins of this large blocked pattern across Europe can be traced back to the appearance of two individual regions of mid-latitude blocking over central Russia and the Bering Sea in mid January. Over the next two weeks, these two regions merged together to form the ‘block’ we see now.

The appearance of significant blocking after a long absence is reflected in the strong decline of the Arctic Oscillation (AO) index, which effectively describes a state in the atmosphere where the flow of westerly winds is either stronger or weaker than usual in the northern hemisphere. It is currently in its negative phase, meaning the westerly flow is less strong than normal. The switch to a negative AO was seen in late January and highlights the dramatic change from generally strong westerly flow to the much less westerly or even easterly blocked state.   

Despite the general unpredictability of blocking patterns, there were potential signs of an increased risk of a significant cold weather several weeks ago when the high altitude winds began to weaken in longer-range forecasts. We now understand that there is a clear link between the weakening of these high altitude winds and the surface weather that operates on monthly timescales and in situations like this it can provide a ‘window of opportunity’ for monthly forecasts to warn of increased risk. Based on this understanding, the Met Office 16 to 30 day forecast has reflected the increasing risk of cold conditions since mid January.

Met Office Hadley Centre scientists have investigated and demonstrated a clear stratospheric influence on surface climate during these events, with easterly winds burrowing down through the atmosphere to affect the jet stream and surface climate. The result is a switch from mild westerly Atlantic flow over Europe to easterly winds with an increased risk of cold extremes.

Weakening of the jet stream in the Stratosphere can allow easterly winds to move down through the atmosphere to give cold easterly winds at the surface. This can result in cold and snowy weather across the UK.

A similar situation occurred at this time of year in 2009 when we had significant snowfall across the UK and other parts of Europe, following a strong breakdown of the high altitude jet. Although only some cold winter spells can be predicted in this way, other recent winters such as 2006 and 2010 have also shown clear examples of the effect.





Met Office in the Media: 29 January 2012

29 01 2012

Today the Mail on Sunday published a story written by David Rose entitled “Forget global warming – it’s Cycle 25 we need to worry about”.

This article includes numerous errors in the reporting of published peer reviewed science undertaken by the Met Office Hadley Centre and for Mr. Rose to suggest that the latest global temperatures available show no warming in the last 15 years is entirely misleading.

Despite the Met Office having spoken to David Rose ahead of the publication of the story, he has chosen to not fully include the answers we gave him to questions around decadal projections produced by the Met Office or his belief that we have seen no warming since 1997.

For clarity I have included our full response to David Rose below:A spokesman for the Met Office said: “The ten year projection remains groundbreaking science. The complete period for the original projection is not over yet and these projections are regularly updated to take account of the most recent data.
“The projections are probabilistic in nature, and no individual forecast should be taken in isolation. Instead, several decades of data will be needed to assess the robustness of the projections.

“However, what is absolutely clear is that we have continued to see a trend of warming, with the decade of 2000-2009 being clearly the warmest in the instrumental record going back to 1850. Depending on which temperature records you use, 2010 was the warmest year on record  for NOAA NCDC and NASA GISS, and the second warmest on record in HadCRUT3.”

Global average temperatures from 1850 to 2011 from the three individual global temperature datasets (Met Office/UEA HadCRUT3, NASA GISS and NOAA NCDC

Furthermore despite criticism of a paper published by the Met Office he chose not to ask us to respond to his misconceptions. The study in question, supported by many others, provides an insight into the sensitivity of our climate to changes in the output of the sun.

It confirmed that although solar output is likely to reduce over the next 90 years this will not substantially delay expected increases in global temperatures caused by greenhouse gases. The study found that the expected decrease in solar activity would only most likely cause a reduction in global temperatures of 0.08 °C. This compares to an expected warming of about 2.5 °C over the same period due to greenhouse gases (according to the IPCC’s B2 scenario for greenhouse gas emissions that does not involve efforts to mitigate emissions).  In addition the study also showed that if solar output reduced below that seen in the Maunder Minimum – a period between 1645 and 1715 when solar activity was at its lowest observed level – the global temperature reduction would be 0.13C.





Climate change and extreme weather

4 12 2011

As the first week of COP17 in Durban draws to a close Peter Stott, Head of Climate Monitoring and Attribution at the Met Office Hadley Centre was interviewed by OneWorld TV about how our climate is changing today and what this means for the risks of extreme weather around the world.

The Met Office is at the UN Climate Change Conference supporting the UK Department for Energy and Climate Change in it’s negotiations on behalf of the UK. This means that we provide independent scientific advice on which sound negotiations can be based.

Whilst here at COP17, our scientists have also been working with the UN World Food Programme exploring food security issues in Africa today and in the future. Our scientists have also been speaking with other African scientists about the science of climate change for their own countries and how we can work together on issues such as understanding regional climate change, regional climate modelling and developing robust long-range forecasts on which many people in these countries rely.





Met Office in the Media: 01 July 2011

1 07 2011

The Independent has today reported about a partnership between the Met Office and NCAR and other leading climate scientists to investigate exceptional weather events to see whether they can be attributable to global warming caused by greenhouse gas emissions. In ‘Extreme weather link ‘can no longer be ignored’ Steve Connor reports on the Attribution of Climate-related Events (ACE) project which held its first workshop in August 2010 in Colorado.

Peter Stott, Head of Climate Monitoring and Attribution at the Met Office Hadley Centre said:  “We’ve certainly moved beyond the point of saying that we can’t say anything about attributing extreme weather events to climate change. It’s very clear we’re in a changed climate now which means there’s more moisture in the atmosphere and the potential for stronger storms and heavier rainfall is clearly there.”

More information on this work can be found in:

Climate change: how to play our hand? (Guardian)
Pakistan floods – More than just an active monsoon? (Met Office News Blog)

Elsewhere the Daily Mail and other papers have reported on a research paper that has suggested that aircraft taking off and landing increase the amount of snow or rainfall around airports, where due to the variability in weather is likely to mask any phenomenon within the observations.

 

 





Met Office Chief Scientist nominated for Public Servant of the Year in Women in Public Life Awards

7 06 2011

Prof. Julia Slingo OBE has been nominated for Public Servant of the Year in Women in Public Life Awards 2011.

Her citation from the Women in Public Life Awards says:

Professor Julia Slingo OBE is widely recognised as a world-leading scientist in her own right. Since February 2009 she has served as Met Office Chief Scientist providing inspirational leadership of science in the Met Office, and in the wider UK and international community. A leading authority on weather and climate science, she frequently speaks to her peers, the media and the public to promote a common understanding of the issues and impacts associated with natural hazards, weather and climate science. Her previous roles include Director of Climate Research in the National Centre for Atmospheric Science where she led climate research from UK academic institutions, and Founding Director of the Walker Institute for Climate System Research at the University of Reading. Julia is also the first woman to be President of the Royal Meteorological Society, a post she held since 2008.

‘Julia is one of very few women to join the influential group of Government chief scientific advisers. Last year’s volcanic eruption in Iceland and subsequent closure of European airspace provided a keen test of her leadership and communication skills, in providing the scientific advice underpinning the UK’s response to the crisis. Throughout this rapidly changing event, she provided Government with expert advice on the distribution of volcanic ash across international airspace. She also provided the leadership needed to quickly implement new science to meet the changing requirements of the aviation community. Importantly, despite considerable pressure from the media and a number of understandably worried airlines, Julia ensured advice was impartial, evidence based and delivered with the highest scientific integrity. This has been acknowledged through a Select Committee enquiry. Julia’s passion and drive for her science, and its impacts on people, is infectious. This passion is never more evident than when she is briefing and advising Government officials and politicians, or speaking in the media. In the last year she has, for example, appeared on BBC Newsnight and provided an authoritative voice for the Independent and Nature on a range of subjects including the flooding in Pakistan and Australia, and the cold winter conditions in the UK. Recognising Julia’s major role during an unprecedented year of global natural hazards, the American Geophysical Union invited her to deliver the prestigious AGU Frontiers of Geophysics keynote lecture to its annual conference in December 2010.’

The Awards celebrate women leaders in society and seek to recognise and promote the work of women in politics, business, the civil service and community leadership. The ceremony will take place on 13 September.





Met Office issues Atlantic tropical storm forecast for the 2011 season

26 05 2011

Our forecast for this year’s North Atlantic tropical storm season states it is likely to be quieter than 2010, with 13 tropical storms between June and November 2011, with a 70% chance that the number will be in the range 10 to 17.

This is very close to the 1980-2010 long-term average of 12, and is in contrast to 2010 which had a total of 19 tropical storms.

Tropical storm frequency forecast. June to November 2011

Tropical storm frequency forecast. June to November 2011

The most likely Accumulated Cyclone Energy (ACE) index – a measure of the storm lifetimes and intensities as well as total numbers over a season – is 151, with a 70% chance that the index will be in the range 89 to 212: well above the 1980-2010 average of 104.

Accumulated Cyclone Energy (ACE) Index. forecast  June to November 2011

Accumulated Cyclone Energy (ACE) Index forecast . June to November 2011

For the past four years, the Met Office forecast has given accurate guidance of Atlantic tropical cyclone activity, identifying the relatively quiet seasons of 2007 and 2009 from the active seasons of 2008 and 2010.

Matt Huddleston, Principal Consultant on climate change at the Met Office said: “North Atlantic tropical storms affect all of us through fluctuating oil, food and insurance markets. Seasonal and multi-year forecasts are the focus for key research at the Met Office and the benefits of that are being realised through the increasing accuracy of its predictions”.

This is the second year of operation of the Met Office’s new seasonal prediction system called GloSea4. The new generation model has better representation of the complex physical processes that cause tropical storms and hurricanes to form, thus improving the accuracy of the forecast. The forecast also uses information from the seasonal prediction system of the European Centre for Medium Range Weather Forecasts.

One of the key indicators for a tropical storm season is the El Niño Southern Oscillation (ENSO), which affects sea surface temperatures in the tropical Pacific and, remotely, conditions in the North Atlantic. It’s therefore vital to be able to accurately predict the ENSO cycle and GloSea4 has shown good skill in such predictions.





Met Office in the News: Friday 18th February

18 02 2011

Earlier this week the journal Nature published a paper in how emissions of greenhouse gases increased the odds of the Autumn 2000 floods.  This paper used the detailed computer climate model developed at the Met Office Hadley Centre. Using this the project team simulated the weather in Autumn 2000, both as it was, and as it might have been had there been no greenhouse gas emissions since the beginning of the 20th century. This was then repeated thousands of times using a global volunteer network of personal computers participating in the climateprediction.net project in order to pin down the impact of emissions on extreme weather. The team then fed the output from these weather simulations into a flood model, and found that 20th century greenhouse gas emissions very likely increased the chances of floods occurring in autumn 2000 by more than 20%; and likely by 90% (close to doubling the odds) or more.

Scientific evidence

Lord Henley, Environment Minister, said: “I welcome this research which is the first to attribute how rising greenhouse gas concentrations may increase the chance of a particular flood. This work reinforces the scientific evidence on the need for the UK to tackle climate change, and to increase our resilience to the challenges climate change will bring from extreme weather events.”

Dr Peter Stott, of the Met Office, and a co-author of the report, said: “This study is the first step toward near real-time attribution of extreme weather, untangling natural variability from man-made climate change. This research establishes a methodology that can answer the question about how the odds of particular weather events may be altering. It will also allow us to say, shortly after it has occurred, if a specific weather event has been made more likely by climate change, and equally importantly if it has not.”

Developing the science

The Met Office Hadley Centre has been commissioned by DECC, Defra and DfID to work with international partners as part of the Attribution of Climate-related Events Group. The group is developing the science of attribution of extreme weather that will be needed to provide regular and scientifically robust assessments of how the odds of these phenomena are changing.

 

Ocean Forecasting Success

Met Office scientists have been awarded the Denny Medal for the best research paper of 2010 by the Journal of Operational Oceanography. The paper describes how the Met Office operational Forecasting Ocean Assimilation Model (FOAM) and the new Nucleus for European Modelling of the Ocean (NEMO) work and presents verification of their performance.

FOAM data of the three dimensional density structure of the ocean were primarily used by the Royal Navy in their sonar propagation models for use in anti-submarine warfare. From this original use, the model has been developed to provide both our government and commercial customers with forecasts that include:

  • Ocean currents
  • Salinity
  • Ocean surface temperatures
  • Sea-ice extent

Such forecasts are critical to sensitive offshore operations such as oil and gas drilling and undersea cable repair and demonstrates how the Met Office supports both our government, defence and commercial customers.





Met Office in the Media: 14 December 2010

14 12 2010

The current cold weather continues to feature across the media, with widespread coverage of the predicted return to arctic conditions on Thursday this week.  The Guardian reports that the ‘Weather set to take Arctic turn as big freeze returns to Britain’ whilst the Telegraph reports that ‘The second Big Chill set to last a month‘‎. Wales online have reported ‘Arctic blast blowing in on Thursday‘, whilst in Scotland, where there is the risk of significant snow showers in northern and western parts through Thursday and Friday, The Scotsman warns of ‘The disruption: Motorists warned to expect black Thursday’.

There has been much discussion today about whether we will see a White Christmas this year, with some other forecasters coming out and saying it is “guaranteed”. Most weather forecasters would agree that nothing is ever guaranteed in meteorology and regarding whether it will snow on December 25th it is still too early to provide a detailed forecast. More information is in a post made yesterday on a White Christmas.

Elsewhere there has been widespread coverage of new research by Met Office scientists on using lightning to measure the height of the plume emitted from erupting volcanoes. It is hoped this can be used to help in forecasting ash plume movements. EnvironmentalResearchWeb reported that ‘Volcanic lightning could help monitor plume height‘, along with MSNBC and The Economist.

We have also released verification of our North Atlantic Hurricane season forecast this week. The Met Office accurately predicted the above-average North Atlantic tropical storm season again this year, maintaining the excellent record of its forecast since it was introduced in 2007, and more detail can be found in ‘Continued success for tropical storm forecast’.

Finally, The Armstrong and Miller Show on BBC One on Saturday night used Met Office graphics to support a sketch about the difference between weather and climate. Ben Miller gave us a timely reminder that what is happening outside the window right now is ‘weather’, and the long-term trend averaged over many years is the ‘climate’. You can watch this on BBC iPlayer starting at 7 minutes and 5 seconds in.





Met Office Chief Scientist at the AGU Autumn Meeting

14 12 2010

The Moscone Conference Center, location of the AGU Fall Meeting

The Moscone Convention Center, location of the AGU Fall Meeting

They say that this is the biggest science meeting of any year and with just one look at the crowds surrounding the 2010 meeting in San Francisco it’s hard to argue against that.

Over 15,000 scientists representing every colour and creed of the geophysical disciplines are gathered at the huge Moscone Convention Center to deliver and debate the big topics of the moment.

The Met Office‘s Julia Slingo is among them. Our Chief Scientist is here at the American Geophysical Union Fall Meeting to deliver a presentation on what she sees as the scientific challenges facing society in making us more resilient to natural hazards.

We live a lifestyle that makes us increasingly vulnerable to all sorts of hazards, be they related to extreme weather or geological phenomenon such as the Eyjafjallajökull eruption. 2010 has provided the world with many examples of just how exposed we are to these kinds of event.

As well as that volcanic eruption that had such a devastating impact on air travel right across the world, extreme rainfall in Pakistan and China and record-breaking temperatures in Russia this past summer have caused tragically high loss of life and massive damage to the infrastructure of those countries. And currently the UK is in the grip of its worst early winter for many years. So what can be done to address this? 

In her talk, Professor Slingo says we need to be able combine work from different areas of science and deliver increased computing capacity to provide better answers to the problems faced by society today.

But more than this it is imperative we look at what computer weather and climate prediction models tell us in a different way. We should focus more on making a quantified assessment of the probability of a certain outcome so that we can provide the sort of advice needed to combat what may be an increasing frequency of such dangerous weather.

And while our models are by no means the finished article they do tell us some things well enough. High temperatures across parts of Russia were clearly signalled by seasonal prediction models and the risk of record-breaking extremes was identified in a small, but significant, number of the ensemble members.

Professor Slingo believes we have the basic building blocks required to deliver better predictions of weather extremes, but it is becoming increasingly obvious we need to link different scientific disciplines to fully counter the threats posed by them. Our increasing vulnerability makes that vital.





Near record temperatures in 2010 to be followed by cooler 2011

2 12 2010

Global temperature has warmed to near record levels in 2010 say climate scientists from the Met Office and the University of East Anglia. Provisional figures for the three main global temperature datasets put 2010 on track to become first or second warmest in the instrumental record.

The preliminary figure for January to October 2010 is 0.52 °C above the long-term average on the Met Office – Climatic Research Unit (HadCRUT3) dataset, placing it equal with the record-breaking 1998. 

The Met Office annual global temperature forecast for 2010, Climate could warm to record levels in 2010, issued at the COP15 talks in Copenhagen, predicted that the year was “more likely than not” to be the warmest year. Dr Adam Scaife, head of long range forecasting at the Met Office said, “The three leading global temperature datasets show that, so far, 2010 is clearly warmer than 2009 despite El Niño declining and being replaced by a very strong La Niña, which has a cooling effect.”

Although La Niña has stabilised, it is still expected to affect global temperature through the coming year. This effect is small compared to the total accrued global warming to date, but it does mean that 2011 is unlikely to be a record year according to the Met Office prediction based on the three main datasets. Nevertheless an anomaly of 0.44 °C is still likely — with the range very likely to be between 0.28 °C and 0.60 °C. The middle of this range would place 2011 among the top 10 warmest years on the record.

Dr Vicky Pope, the Met Office’s head of climate science advice said, “Our annual prediction of global temperatures for the next year combined with our monitoring of the observed climate helps people to put the world’s current climate into context.”

More information is available at http://www.metoffice.gov.uk/corporate/pressoffice/2010/pr20101202b.html








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