The solar cycle and space weather 

You may have noticed solar flares, sun spots and coronal mass ejections have been in the news this week, following a space weather event which led to aurora borealis sightings in some northern parts of the UK between the cloudy weather. While the event itself was moderate, it does showcase the move to a new solar cycle, as Met Office Space Weather Forecaster Krista Hammond explains in this blog. 

The number of sunspots visible on the sun varies over a roughly 11-year period from one peak to the next, known as the solar cycle. The peak in sunspot frequency is referred to as solar maximum, whilst the period during which we see the fewest sunspots is known as solar minimum.   

Sunspots are areas of intensely concentrated magnetic field on the sun’s surface. This causes them to be cooler than the surrounding area (the photosphere), and so they appear darker. Sunspots vary in magnetic complexity as well as size – the largest sunspot regions, often referred to as active regions, can be many times the size of the Earth.   

Sunspots are important in space weather forecasting as they tend to be the origin of space weather phenomena that can have an impact at Earth, namely solar flares, solar radiation storms and coronal mass ejections (CMEs).  

The Met Office Space Weather Operations Centre is monitoring the sun’s activity 365 days a year

Solar flares are sudden releases of energy across the entire electromagnetic spectrum. They are hard to predict, and the energy can be detected in Earth’s atmosphere as soon as 8.5 minutes after the occurrence of a solar flare. In association with large flares, solar radiation storms may also occur. These consist of high energy charged particles, predominantly electrons and protons, and typically take between 10 minutes and several hours to arrive at Earth.  

A CME, also often associated with a flare, is the ejection of material from the sun into interplanetary space. If the material is directed towards the Earth then the event may result in a disturbance to the Earth’s magnetic field and ionosphere. They can take days to reach Earth, carrying a local magnetic field from the Sun, and their arrival time is a key focus of space weather forecasting. 

It follows then that since impactful space weather tends to originate from sunspots, the frequency of space weather events shows some correlation with the solar cycle. As we see an increase in the number of sunspots, we also expect to see an increase in space weather activity. The last solar minimum occurred in December 2019, with the next solar maximum expected around 2025. Over the coming years, as we continue towards solar maximum, we can expect to see an increase in the frequency of space weather events.  

Space weather forecasting at the Met Office 

The most recognisable and visible space weather effect is arguably the auroras (Northern and Southern Lights). The geomagnetic storm we have seen over the last few days that has been responsible for the aurora is nothing out of the ordinary, and aside from producing the northern lights will have very little impact on Earth. However, extreme space weather can have an impact upon our technology, national infrastructure, and communications systems. Luckily, these extreme events are very rare. 

As we continue towards solar maximum, we can expect to see an increase in the number of space weather events of a similar magnitude to what we have seen this week. However, the most extreme events that can cause the largest impacts can take place at any point in the 11-year cycle. Therefore, space weather prediction is of crucial importance to many, including the government, satellite operators and the aviation industry, at any point in the solar cycle, day or night. 

This is why the Met Office Space Weather Operations Centre provides 24/7 forecasts and warnings of space weather for Government and responder communities, critical national infrastructure providers and the public, to help them understand the risks and mitigate against the impacts

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The feasibility of calculating an individual’s contribution to extreme weather events

Climate change is making some forms of extreme weather events, such as heatwaves and heavy rainfall, more frequent and more intense.

Communities affected by those events inevitably suffer economic, social and societal impacts. The rising number of extreme weather events – and the losses and damages associated with them – poses a challenging question: who should pay?

This question is part of the so-called Loss and Damage agenda – which will be discussed at COP26 in Glasgow next month. Although the issue has been considered for some time there is currently no agreed method for calculating, apportioning liability or awarding such payments.

Fraser Lott is a Met Office scientist who has been developing scientific techniques to address this problem, in the hope of arriving at an objective solution.

Working with an international team of researchers, Fraser sought to show how the scientific capability of event attribution could be used to establish how individuals’ emissions affect extreme events through climate change. Fraser Lott said: “Event attribution is a climate science technique for calculating the likelihood that an extreme weather event was made more or less likely or severe because of climate change. By combining event attribution with population and emissions data, we realised that it was feasible to begin to calculate an individual’s contribution to a climate change event.”

It is believed to be the first time that anyone has attempted to express the impact of an individual’s emissions on an event based on event attribution: a scientific method of assessing to what extent an extreme event was influenced by individual human activity.

Chinese aquaculture

Aquaculture is an important economic sector in eastern China. Picture: Shutterstock

As a case study, this paper examined the impact of a 2018 heatwave in eastern China on the country’s aquaculture industry, which lost 6.87 billion yuan (around £790 million) as a result of the event. Using data on historical emissions since 1991 – the date when the first international consensus on carbon emissions was reached with the publication of the IPCC’s First Assessment Report – the team examined individuals from four representative nations (Sweden, China, Russia and the USA). The emissions of these countries were then divided equally among their population according to the number of years they had been over 18 (and therefore responsible adults) between 1991 and 2017, the year before the heatwave took place. Using this pioneering methodology, the potential cost to each individual could then be calculated, finding they were responsible for between 0.53 and 18.10 yuan of these aquaculture losses (around 6p to £2). This varied depending on the person’s age and their country’s emissions, showing how the scale of such responsibilities can be greatly affected by national development and demographics.

Fraser added: “As you’d expect with a newly-developed technique, our research doesn’t provide an answer to every situation and there are further issues and challenges which subsequent research will need to address. We believe it is especially important that a broader range of experts such as philosophers, ethicists, policy experts and economists assist with the continued development of this emerging research.”

The team noted that, if this technique were extended to cover multiple events, changes in the probabilities of events which did not occur because of climate change would also have to be factored into any cost calculation. Countries with weather which is difficult to simulate or with insufficient climate observations would also present challenges when assuring any payment system was fair: there are established techniques which can counter these issues.

The issue of Loss and Damage is very broad and this research does not take full account of important aspects contributing to the costs of extreme weather events including the exposure of people to the hazards of extreme weather events or their vulnerability. The team also acknowledge that there are many demographic factors other than nationality and age which could influence an individual’s contribution to extreme weather events.

Fraser added: “The preliminary approach in our paper has demonstrated that it’s possible to calculate an individual’s contribution by using the available climate and population data: how this develops will be a matter of discussion and debate by experts and the public.”

The paper – Quantifying the contribution of an individual to making extreme weather events more likely – is published today (12 October, 2021) in the journal Environmental Research Letters

The research also involved the following authors:

  • Andrew D King of the School of Geography, Earth and Atmospheric Sciences, University of Melbourne, Australia
  • Simon F B Tett of the School of Geosciences, University of Edinburgh, Edinburgh, United Kingdom
  • Dongqian Wang of the National Climate Center, China Meteorological Administration, Beijing, People’s Republic of China
  • Andrew Ciavarella, John J Kennedy and Peter A Stott of the Met Office
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A look back at the successes of WISER 2

As the second phase of the Weather and Climate Information Services for Africa (WISER) Programme comes to a close, Met Office WISER Programme Manager Kate Ferguson gives an overview of the achievements and learnings from the programme.

I first wrote a blog for the Weather and Climate Information Services for Africa (WISER) Programme just after I joined as Programme Manager back in January 2020. The landscape was very different then, we were mid-implementation with projects in full swing, pushing to reach their targets, and COVID-19 and all its complications was something yet to come our way.

Now WISER as we know it is closing its second phase, we have the chance to look back, not just to that more ‘ordinary’ time, but to where it all began. In 2015, a scoping study – CIASA – was carried out to provide a snapshot of the state of climate services in Africa and outlined gaps that could be addressed. From this, WISER was born. Phase 1 was delivered through 5 ‘quick start’ projects, and these brief but intense projects formed the foundation, learning and direction that became WISER Phase 2.

There is no doubt that the ambition of WISER 2 was immense, with hugely ambitious targets to build on what was achieved through Phase 1, but also to scale that up to cover much of East Africa and grow to 12 projects – some of them with multi-million budgets, some working in extremely complex political and security context and some with much smaller budgets, testing out completely innovate approaches to reaching end users. At its heart, WISER strives to make a difference to millions of people across East Africa, by enhancing their resilience to weather and climate related shocks and improving regional economic development, which is something we are proud to be able to demonstrate.

Co-production is the foundation of WISER – bringing together the science and the end users of weather and climate information to enable better decision making. It’s a huge achievement that the programme has reached 3.3m households with new or improved climate services as a result of this co-production approach. In addition, we now know that the programme has contributed over £200m of avoided losses across East Africa due to the use of climate information. We also know that a lot of the activities carried out have been sustained even after the funding period ended – which is the best legacy you can ask for.

The purpose of the HIGHWAY project was to deliver the provision of regular weather forecasts and severe weather warnings for fishing boats and small transport vessels on Lake Victoria.

As the programme draws to a close, we have naturally been making space to reflect on what has worked well and what could be improved in the future. A series of learning briefs have been produced, and a programme lesson and recommendation summary. There are too many to mention here, but a few key lessons identified across WISER are:

  • Projects have a greater impact when they are aligned to national and regional development priorities, future deigns need to be based around and embedded within these to be complementary.
  • Measuring the socio-economic benefit of a project is an extremely helpful tool to support National Meteorological and Hydrological Services to promote the value of taking a co-production approach and meeting the needs of their users, supporting them to secure future investment and national government budget allocations.
  • Project and programme design needs to be gender-sensitive to be able to consider the inequalities within climate services, and adapt to meet the needs of the most vulnerable and have the greatest impact.

WISER has been the testing ground for many new and innovative project approaches and methodologies, with vast amounts of learning along the way. The aim now is to feed this learning into back into the weather and climate sector, to support future projects and programmes to build on the successes of WISER so far.

Between now and the end of 2021, we will produce a number of resources that can support this, and respond to the programme learnings with a revised, shorter more focused socio economic guidance, a programme level Gender Action Plan to support future project and programme design, a sustainability toolkit to assess what has been ‘left behind’ once funding ends, and of course, a new CIASA report, that will bring together all that has been achieved in the last 6 years, and provide direction for future interventions by identifying remaining gaps within the weather and climate sector in Sub-Saharan Africa.

To find out more about the impacts of WISER as Phase 2 closes, read our news release here.

To find out more about the WISER programme, including the phase 1 and phase 2 projects and learnings, discover our webpages here.

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Arctic sea ice decline continues, with 2021 the 12th lowest summer minimum extent on record

On 16 September 2021, Arctic sea ice reached its annual minimum extent, signifying the end of the summer melting period. According to the National Snow and Ice Data centre (NSIDC), Arctic sea ice extent stood at 4.72 million square kilometres on 16 September, which is the 12th lowest September minimum on record since satellite observations began in 1979.

The extent of Arctic sea ice has on average been declining over the last thirty years, reaching its annual minimum every year in September. Whilst this year is higher than the record low sea ice extent of 3.41 million square kilometres reached in 2012, it is still around 25% lower than the long-term (1981-2010) average of 6.33 million square kilometres.

Arctic summer sea ice extent is naturally influenced by changing weather patterns, such as temperature, cloud cover, summer storms and wind patterns. Whilst this can cause fluctuations in sea ice extent from year to year, when comparing recent satellite observational records there is a clear and significant downward trend.

Manager of the Met Office Polar Climate Group, Ed Blockley, said:“Although this year’s minimum sea ice extent is not record-breaking, it is yet another year that sea ice extent has continued to follow the prevailing long-term trend of decline. We have seen a sustained long-term decline in Arctic sea ice cover over the last 4 decades, which is most pronounced at the summer minimum in September. Although there are year-to-year variations associated with the weather in individual years, we have lost, on average, around 87,000 square km of September sea ice extent each year, an area more than 4 times the size of Wales!

“Sea ice is a significant part of our climate system, and it can be heavily impacted by even minor changes in temperature. We can see these changes in the annual cycle of sea ice melt and growth, where ice is starting to melt earlier in the spring and freeze-up later in the autumn.“As global temperatures continue to increase, the Arctic is likely to heat up faster than the planet due to polar amplification. So it is really important to pay close attention to these broader trends that tell us our climate is changing.”

You can find out more about Arctic sea ice and look out for our upcoming Arctic and Antarctic end of season report here.

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Met Office science: narrowing the range of climate uncertainty

The United Nations has today (Thursday 16 September, 2021) published a synthesis report on the perils of climate change and the need for urgent climate action.

The report features hard-hitting forewords from both Antonio Guterres – Secretary-General of the United Nations – and Prof Peter Talaas – Secretary-General of the World Meteorological Organization.

The United in Science 2021 report draws heavily on the latest scientific evidence, including pivotal findings from the Met Office.

Arctic weather station
Obtaining meteorological information from fast-changing regions like the Arctic provides greater granularity on the scale of the changing climate. Pic: Shutterstock

Professor Adam Scaife is one of the key Met Office contributors to the report. He said: “2021 is a vital year for climate change, as decision makers assemble in November in Glasgow for COP26. Everyone knows that many hopes are pinned on the final outcomes from the conference, but before decision makers can begin to agree meaningful action, it is vital for them to have access to the best-available climate data and predictions.”

The Met Office’s contribution to the report has concentrated on two principal areas: monitoring of global temperature and sea ice; and narrowing the uncertainty about what will happen to the climate in the next few years.

Adam Scaife continued: “The earth’s temperature is continuing to rise and as decision makers continue to decide on future policies to avert the worst outcomes of climate change and stay on a pathway within Paris Agreement limits, they require the best scientific information available.”

In an attempt to understand more about the latest global temperature rises and what will happen over the next five years, Met Office scientists continue to develop capacity in the science of observing and predicting variations in our climate.

For predicting climate in the near term, the Met Office Hadley Centre leads the World Meteorological Organisation’s effort to combine multiyear predictions from the best computer models available. Professor Scaife said: “This synthesis report takes the very latest observations and predictions and gives a stark warning that temporary exceedance of the 1.5°C level is quite possible in the next few years and that unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting long-term warming to 1.5°C will be impossible.”

In December 2020, the Met Office and the University of East Anglia Climate Research Unit announced a series of key improvements to their long-running global temperature data set, HadCRUT, which contains data stretching back to 1850.

HadCRUT brings together measurements of near-surface air temperature made at weather stations around the world with measurements of the temperature of the top-most layer of the ocean (or sea-surface temperature). The updates to HadCRUT (now known as HadCRUT5) include:

  • updated adjustments to handle the changing biases between different ways of measuring sea-surface temperatures over time;
  • A significant increase in the number of weather stations used over land;
  • Using statistical methods to extend the data set’s coverage in the early record and in areas that are still data-sparse today, including the rapidly warming Arctic. This provides more accurate estimates of global, hemispheric and regional temperature changes.

John Kennedy of the Met Office Hadley Centre said: “These revisions show slightly more warming in recent times, compared with previous iterations of the data set. The new data set provides decision makers with our best estimate yet of the rate of warming and its uncertainty and also serves as a reminder that the world has warmed considerably since 1850.”

The United in Science 2021 report, the third in a series, is coordinated by the World Meteorological Organization (WMO), with input from the UN Environment Programme (UNEP), the World Health Organization (WHO), the Intergovernmental Panel on Climate Change (IPCC), the Global Carbon Project (GCP), the World Climate Research Programme (WCRP) and the Met Office (UK).

The United in Science report provides details on:

  • Greenhouse Gas Concentrations in the Atmosphere (WMO)
  • Global greenhouse gas emissions and budgets (Global Carbon Project)
  • Emissions Gap (UN Environment Programme)
  • Global Climate in 2017-2021 and 2021-2025 (WMO, UK Met Office)
  • Highlights of the Intergovernmental Panel on Climate Change Sixth Assessment Report – the Physical Science basis
  • Sea level rise and coastal impacts (World Climate Research Programme)
  • Heatwaves, widlfires and air pollution (World Health Organization/WMO)
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How will Hurricane Larry influence the UK’s weather?  

The hurricane season in the Tropical North Atlantic frequently plays a role in dictating the state of play with the UK’s dominant weather patterns, but with various stories circulating in the media about ex-Hurricane Larry’s influence over the forecast, we thought we’d clear up the current picture from across the Atlantic Ocean.  

Hurricane Larry struck North America last week as a Category 1 hurricane and brought widespread disruption to Newfoundland and Greenland before moving out to sea. The breakdown of Larry late on Friday led to some significant uncertainty in the forecasts for the UK, as conditions in the west of the Atlantic often help to drive the weather we see in the UK. It’s this uncertainty that led to some reports of warmer weather to come, but that isn’t the case on this occasion as Larry’s influence on our weather weakens from now on.  

Ex-Hurricane Larry’s influence over the UK weather is somewhat confined to helping to keep our current unsettled weather pattern in place and fairly slow moving. The remnants of Larry are now loosely aligned with a low pressure to the south of Greenland and is set to have little impact on the medium and long term forecasts for the UK.  

Aidan McGivern gives Monday evening’s Met Office forecast for the UK

As the UK’s current weather pattern develops later in the week, some warmer air will be drawn in from the south, but this will be associated with some thick cloud and, at times, heavy rain. This isn’t linked to the remnants of Larry in the North of the Atlantic.  

Met Office Deputy Chief Meteorologist Adam Thornhill said, “One of the main impacts of ex-Hurricane Larry on the UK weather has been the uncertainty it brought to the forecast over the past weekend. Hurricanes that affect North America often play a role in the UK’s weather when they move into the North Atlantic.  However, the way Larry transitioned from a Hurricane into a North Atlantic low, means its impacts on the UK’s weather systems were and are limited to holding some of our unsettled weather in place into the middle of this week.  

“Ex-Hurricane Larry no longer exists, but the low which has some legacy ‘Larry’ air, has moved to the south of Greenland and is set to have little impact on us in the UK as it continues to lose intensity and move into the Arctic Sea.  Although there may be some warmer air moving across the southeast of England through Tuesday and Wednesday, any temperature rise is likely to be subdued with some thick cloud and rain at times. Some sunny spells are most likely on Thursday, where temperatures in the East and Southeast of England may reach the mid-twenties before another band of rain moves east across the UK later Thursday and through Friday.” 

The high pressure moving into the south from Thursday could bring temperatures to the low or mid 20s in the southeast where there’s the best of the sunshine, but cloud will likely subdue temperatures in other areas before some more unsettled weather moves in from the west.  

Get the latest forecast on the Met Office website.  

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Will Hurricane Ida affect the UK’s weather?

Hurricane Ida has seen winds of up to 150mph and intense rainfall bringing widespread flash flooding to a swathe of America, in what has been the fifth strongest storm to hit the US mainland.

Ida formed over the Caribbean Sea at the end of August, and then moved north westwards becoming a tropical storm. As Ida moved over the Gulf of Mexico it tracked across a deep area of warm water and developed rapidly into a Category 4 Hurricane and made landfall over Louisiana on Sunday evening, UK time. After making landfall Ida started to lose her strength; like all hurricanes, she drew her energy from warm seas. However, although Ida’s winds quickly eased, she has (as forecast) continued to bring a trail of extreme rainfall to the north-eastern United States, notably New York. The heavy rainfall lasts longer and can affect more people than the damaging winds do.

Hurricane Ida has been the fifth strongest hurricane to make landfall on the mainland of the United States.

Impacts in the US from Ida have been severe, with reports of at least three inches of rain falling in New York’s Central Park within an hour and Louisiana seeing similarly devastating conditions earlier in the week. One million are reported to be without power, and sadly there have been a high number of fatalities.

Met Office Expert Operational Meteorologist Chris Almond, said: “The sheer amount of rainfall within this warm tropical air saw fairly widespread totals of 150 to 250 millimeters, which fell over a couple of days, and is quite exceptional in itself. But Central Park in New York actually recorded 80 millimeters in just one hour, which is a phenomenal amount of rain. That’s nearly over a month’s worth of rainfall in just an hour, and almost double the previous record, which was around 50 millimeters in an hour: and that was only set earlier in August. It has been an exceptional spell of weather for parts of the southern and eastern parts of the United States.”

While Ida’s affects are still being felt across America, bringing a deluge of rain and continued strong winds, some are now wondering if Ida will travel across the Atlantic and impact on the UK’s weather.

In short, no, not directly. But, as is often the case in the North Atlantic hurricane season, the set up in North America can have an influence on the dominant weather we’re likely to see in the UK because of the effects it can have on the jet stream, which straddles the Atlantic and drives a lot of the UK’s weather.

In recent days, the UK has been under the influence of a high-pressure system (a ‘blocking high’ set up). This has seen largely benign weather over the UK, with relatively dry conditions, along with spells of sunshine, but more prolonged cloud for some.

According to Met Office models, Ida is set to break up when it enters the Atlantic and is very unlikely to travel across the ocean intact. However, it will have an influence on the position and strength of the jet stream across the Atlantic – currently the jet stream is very weak, but it will strengthen as the remnants of Ida move northeast away from North America.  The strength of the jet stream can be determined by the temperatures on either side of the flow, with cool air to the north and warm air to the south. When the temperature contrast is greater, such as now with Ida bringing a lot of warm air to the south, the jet becomes more energised. The direction the jet stream then takes will help determine weather patterns for the UK this weekend, with a more northerly position helping to hold high pressure close to the UK.

Met Office Expert Operational Meteorologist David Oliver said: “Ida has obviously had some significant impacts in the US, but that weather system is not expected to travel across the Atlantic and reach the UK as an active system.

“However, it is common for the hurricane season in North America to play a factor in the weather patterns affecting the UK, and in most cases that’s down to its role in shifting the upper air that drives our weather systems.

Hurricanes have a major impact on the transport of heat and moisture from the tropics into the North Atlantic.

David added: “As Ida breaks up, the low-pressure system and warm tropical air associated with it will help to accelerate and shift the jet stream over the Atlantic. The behaviour of the jet stream is complex but overall it will tend to lie to the north of the UK, this helping to hold high pressure close by. So, whilst rain is likely to spread to some northern parts of the UK on Sunday and into Monday, for many places conditions will remain dry and increasingly warm this weekend and into the first half of next week.”

A shift toward more widely unsettled weather isn’t currently expected until later next week as the high pressure finally gets unseated from its current position close to the UK.

Check the latest Met Office forecast on the Met Office website, app or on social media.

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Notably warm summer so far for UK – but not for everyone

The summer so far has been around 1°C warmer than average for the UK, which would potentially place it within the top ten warmest summers on record, but it’s still too early to make a confident statement about final rankings. This may come as a surprise to some, especially for those in the southeast and London, who have had a much wetter and duller summer than average, with many areas seeing more than 50% more rainfall than their long-term averages.  

With a few days still to go until the full figures are published for summer 2021 at the start of September, high temperatures in Scotland and Northern Ireland have helped pull the UK to within the top 10 for warmest summers according to mean temperature, with still some room for manoeuvre before the season is out. The UK has a mean temperature for summer around a degree higher than the average, currently sat at 15.4°C, with still some time to change.  

Map of the UK showing average mean temperatures for summer so far in the UK. The map shows warmer than average conditions in the north of the UK in particular, while slightly cooler in the south.
Average mean temperatures for the UK for summer so far.

In fact, Northern Ireland has so far seen one of its warmer summers using the same measurement (15.0°C), and Scotland (13.8°C) has also been notably warm. Western areas, and especially western Scotland, have also seen much less rainfall than the averages, with Scotland, so far, seeing just 62% (188.1mm) of its average rainfall for the season, and Wales 66% (189.5mm).  

With the best of the dry and warm conditions to be found in northern and western areas of the UK, it has been a markedly different story for the southeast and some southern areas this summer so far.  

Greater London has so far seen an average of 220.2mm of rain, which is 48% more than their long-term average for summer, although not enough to trouble the all-time records for the area. They’re joined by Hampshire (245.2mm, 49% more than average), Surrey (240.3mm, 54% more than average) and West Sussex (250.9mm, 52% more than average) in seeing significantly more rain than their usual summer conditions.  

Map of the UK showing rainfall amounts versus the long term average. The map shows that many northern and western areas have been drier than average, while some areas in the southeast and south have been much wetter than average.
Rainfall amounts versus the long term average for summer so far.

As you might expect, these areas have also seen less of the sun than average, although there is still time in the season for this to shift more with some good spells of sunshine expected before the end of the month.  

Map showing the UK's average sunshine duration. The map shows that the south had been duller than average, but northern areas have already seen more sunshine than average.
Sunshine duration for the UK versus the long term averages

Of course, this summer did see a heatwave in July, which saw the Met Office issue its first ever amber extreme heat warning, as Northern Ireland broke its all-time temperature record on 21 July with 31.3°C recorded at Castlederg. This extended spell of warm weather in July, with stubbornly high night-time temperatures, has helped to lift the averages for the season, with the highest temperatures in that period also seen over western areas, although the rest of the UK was widely warm.  

However, perceptions that summer has been below average for some could come from the fact that August hasn’t yet served up particularly high individual maximum temperatures. So far, the highest temperature recorded this month was at Tyndrum, Scotland with 27.2°C. Only two times in the last ten years has 30°C not been reached in August in the UK and on every occasion in the last 20 years the highest temperature for August was reported in England.  

Temperatures have, however, been fairly consistent over the month of August. So, although there hasn’t been any creeping up past 30°C just yet, the average maximum temperature is actually near to the long-term average at the moment, at 19.1°C. August has also been slightly drier than average so far for most, although some regions are close to or above average such as Northern Ireland, eastern Scotland and parts of southeast England. 

Dr Mark McCarthy of the National Climate Information Centre said, “Obviously there’s still time before the month and season is over, but summer so far is certainly looking drier and warmer than average, that’s despite some of the wet, dull conditions we’ve seen in the southeast in particular.  

“Some of the flooding seen in London in July has seen some individual stations report almost twice their normal summer rainfall but the north and west of the country has experienced plenty of sunshine through June and July, although most of the country has been duller than average through August.” 

Get the latest forecast for the rest of the month on the Met Office website.  

Note: Statistics in this blog are representative of the period to 25 August 2021. The full statistics will be released at the end of the month. Summer, as defined in these statistics, runs from the 1 June.  

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Invoking the oak – nature’s veteran recorder helping scientists understand the rate and scale of climate change

Ancient oak trees – individuals more than 400 years old – extend back into the deep and dark recesses of history.

During that time, these senior trees will have been surrounded by huge fluctuations in climate; to say nothing of the monumental changes in human history and how we have modified landscapes.

For those that can read them, the patterns of tree rings can provide a hint of past seasons, since the growing trees lock in valuable data about the climate for every year of their life.

Oak trees can live for centuries, providing a climate record spanning their lifetime but by monitoring the living tree and recording factors the first appearance of leaves and when the tree becomes bare can provide climatologists with a raft of data the current growing season. During 2020, the growing season for pedunculate oak was extended in the UK by 12 days. Picture: Ted Green/WTML (Woodland Trust media library).

However, that is not the only assistance that oak trees can provide to those researchers looking to understand more about our climate and how it is changing. By observing and charting the changes when individual trees come into leaf or shed their leaves, scientists and climatologists can glean valuable data about fundamental shifts in climate since individual plants respond to the shifting waves of weather and climate patterns from one year to the next.

Meteorologists have often been interested in how the weather and climate have profound impacts on phenology: the study of recurring events in nature and their relationships with climate. And indeed in 1875 the (Royal) Meteorological Society embraced the timing of natural events within the growing interest of phenology.

Dr Debbie Hemming is a Met Office scientist conducting research to improve understanding and modelling of the interactions between vegetation and climate. She said: “Trees and other species are natural data stores. They can be used in so many ways to inform us about the past and present of our changing world.”

With climate change already affecting the world, including the UK, there is a rapidly expanding interest in phenology and how the timing of natural events are responding to climate shifts, like rising temperatures and fluctuations in rainfall patterns.

For 31 years the BAMS Global State of the Climate report has been monitoring climate trends to provide a snapshot of the shifts in global and regional climate. The latest report is published today [25 August 2021] covers 2020.

Using results from phenology studies across the globe, the report states the seasonal cycle of vegetation across the Northern Hemisphere showed a generally earlier spring and later autumn (fall) in 2020 compared to recent decades. These differences were larger across Eurasia than North America.

Debbie Hemming added: “Satellite observations analysed by colleagues at the NASA Ames Research Centre, in the United States, showed that about 55 per cent of the Northern Hemisphere experienced an earlier spring and about 65 per cent a later autumn (fall) in 2020 compared to recent decades.”

Volunteer citizen scientists can make valuable contributions to the understanding of our changing climate by making phenological records. Picture: Michael Hefferman/WTML (Woodland Trust media library).

One UK study – involving citizen scientists from the Woodland Trust’s Nature Calendar project – has been charting the duration of leaves on the pedunculate oak from first leaf to bare tree. The pedunculate oak – colloquially known as the English oak – actually has a range across much of temperate Europe and Asia Minor, and it is the national tree of several European nations, not solely the UK.

Oak trees came into leaf across the UK earlier in 2020 than in any of the previous 20 years.

The average first ‘leaf date’ for the 2000–09 baseline was 26 April (day 116), and average ‘bare tree’ date was 30 November (day 334), giving a 218-day growing season.

Both events are strongly influenced by temperature; the first leaf date advances by approximately six days for every 1°C increase in mean February–April temperature; and the ‘bare tree’ date is  delayed by approximately three days for every 1°C increase in October temperature.

The year 2020, like 2019, had a very warm spring, and this resulted in the earliest United Kingdom first leaf date in the 20-year series (10 days earlier than the in-situ baseline).

October temperature was similar to recent years, and the bare tree date (note these were predicted from the temperature relationship due to COVID-19 monitoring restrictions) was approximately two days later than the baseline.

Professor Tim Sparks, speaking on behalf of the Woodland Trust, said: “The net result was a United Kingdom “oak season” 12 days longer than the baseline. The earlier spring and later autumn (fall) vegetation was associated with warmer than average temperatures during these seasons. Nature is having to keep pace with rapid changes – perhaps never more rapid.

“However, not all species are changing at the same rate. Whilst some species can take advantage of a warmer climate, for others climate change will be a further threat to their existence.”

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Met Office science at the heart of climate assessments

The Met Office Hadley Centre – which celebrated its 30th anniversary last year – has a long and proud history of working and supporting the IPCC. Indeed, one of the foremost scientists who propelled the IPCC, serving as co-chair and chairman of its scientific advisory group from its inception until 2002, was the late Sir John Houghton.

Sir John was Met Office Director General/Chief Executive from 1983-1991 and was instrumental in establishing the Met Office Hadley Centre, which was formerly opened by the then Prime Minister, Baroness Margaret Thatcher, on 25 May 1990. This was the same day that the IPCC First Assessment Report was published.

Professor Peter Stott has been working on climate research at the Met Office since 1996.

Professor Peter Stott joined the Met Office in 1996, a date which coincidentally aligned with the publication of the IPCC’s Second Assessment report. Before the days of widespread email use, Peter remembers fondly that this hefty volume arrived in a large envelope on the doormat at his home just before he started his Met Office career. He said: “Reading through the report, I immediately realised that this was the first official document to make a link between human activities and global warming, using the phrase that there was a discernible human influence on the global climate.”

The following year, Peter attended the global climate conference in Kyoto. Peter said: “Those of us who went were able to present the Met Office Hadley Centre’s work and the conclusions of that second IPCC report.

“It was an important moment because it was when governments first agreed to do something about climate change when they signed the Kyoto Protocol, based largely on the growing evidence from the IPCC’s second report.

“So it was already recognised there was a human influence of greenhouse gas emissions on the climate, but it was still very early days for putting any precision on what that may mean in terms of impacts; such as extreme weather for example.”

Peter added: “Looking back now to the late 1990s our predictions about global warming and global temperature rise were very accurate, even though we weren’t able to rely on the vast supercomputer power that we have today.

“Though, relatively speaking, the information we had from those projections and what it may mean for rising sea levels or agriculture, for example, were very broad brush.”

After two decades of scientific research and increasing technological capability, the sophistication and resolution of climate projections have increased enormously

Peter added: “It is only now with our climate models, that we can simulate climate aspects such as really heavy rainfall and extreme heatwaves at a regional level, putting a local precision on high-impact weather.”

Commenting on the current impacts of climate change, Peter Stott added: “What we are now seeing in 2021 is the very clear effects of climate change playing out in real time, with floods, wildfires and heatwaves.”

The sixth Assessment Report – published on 9 August 2021 – is the first IPCC report to state that it is unequivocal that human influence has warmed the atmosphere, ocean and land.

Peter added: “The latest IPCC report is a big step forward because it is laying out clearly the risks of climate change at least in terms of some of the irreversible impacts of climate such as sea level rise for example which will continue to rise for many centuries. We are still at the early stages of mapping out those risks.

“The better we can understand those risks the better we can mitigate them. That is a big challenge for societies now to be more resilient to heatwaves and other climate risks. The big challenges to come will include being able to provide more information about high-impact climate risks such as heavy rainfall. This is an exciting development that will help us all be better prepared for what is coming at us in the future.

“New scientific information such as the latest IPCC report also helps governments as they seek to reach international agreements to reduce greenhouse gas emissions rapidly enough to avoid the worst effects of climate change.

“This historical and continued contribution the Met Office Hadley Centre has enjoyed with the IPCC acknowledges our status as a world-leading centre for climate science research and has helped to ensure that our observational datasets, climate modelling and peer-reviewed research is incorporated into the heart of the scientific assessments.”

Chris Jones has also recently been selected as an author for a future IPCC report, due for release in 2022. Chris said: “The IPCC represents the “go to” place to understand the state-of-the-science for policy makers and scientists alike. The rigour and comprehensiveness of the assessment brings together experts from all over the world. It’s been a huge honour, and immensely enjoyable, to be a part of this community activity.”

Bringing the Met Office’s journey with the IPCC to a full circle, during the press conference for the latest Sixth Assessment Report (AR6) publication, IPCC Chair, Hoesung Lee, announced that the report is dedicated to the memory of Sir John Houghton.

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