Category: Features

No surprises? The CCC’s latest adaptation progress report

No surprises? The CCC’s latest adaptation progress report

By Kathryn Brown, Head of Adaptation at the Committee on Climate Change Secretariat.

Climate change is a cross-Government issue, and there is still much to do to increase the scale of cross-Government coordination and action to reflect that. As a tranche of new Ministers returns from the summer recess to red boxes full of EU-exit briefing, we will be trying to make our analysis heard. All of our key messages and recommendations are important, but here are three messages from the report that should not be lost amongst the din.

We know what the risks are, and with that comes a responsibility to act

The Government’s own Climate Change Risk Assessment, published every five years, sets out the current and future risks (and some opportunities) from climate change. The latest CCRA is based on the CCC’s Evidence Report, last published in 2016 and currently being updated for release in 2021. It is very clear what the risks to the UK are, from extreme heat, flooding, drought, pests and diseases; affecting both people and wildlife. Recent weather events mirror what is expected and have come as no surprise to the climate science community. The UK’s highest ever recorded temperature of 38.7°C was recorded on 25 July in Cambridge, with similar records having fallen in Belgium, Germany, and the Netherlands in the preceding weeks.  Severe storms and flash flooding have occurred in the north-west and Lincolnshire, with knock-on impacts on infrastructure. Last year saw an extended summer drought. All of these impacts reflect the threats facing the UK from higher temperatures, too much and too little water.

Weather in the UK is becoming more extreme, and sea level continues to rise.

A UK net zero target does not reduce the need for adaptation

To have any chance of meeting the goal of the Paris Agreement (to keep global temperature rise well below 2°C above pre-industrial levels), very ambitious, but very achievable global action to reduce emissions is needed now. To have around a 50% chance of keeping warming below 1.5°C temperature, the latest science suggests that emissions of all greenhouse gases must be reduced and global CO2 emissions need to fall rapidly from today and reach net zero around 2050. The UK’s net-zero target represents an appropriate contribution to those global efforts, but it now must be implemented and other countries must follow suit. Actions to reduce global greenhouse gas emissions taken today will have an effect on some climate hazards in the UK within decades, whilst other hazards (such as sea-level rise) will continue to increase for centuries due to time lags in the climate system. It is highly likely that average annual temperatures in the UK by 2050 will rise by between 0.5 to 2.7°C above a 1980-2000 baseline period, depending on the pathway of global emissions.  What happens beyond 2050 will be influenced even more strongly by global mitigation efforts.

Global average temperature is already around 1°C above pre-industrial temperatures, and rising. Not only do we need to plan adaptation strategies for 2°C, but also for 4°C, which could still be reached based on extrapolations of future global emissions consistent with recent trends. There are going to be limits to adaptation at 4°C, where no action is enough to manage the risk. There also remains the very real risk of triggering ‘global discontinuities’ or tipping points.  The widespread fires happening across the Arctic, and high mortality observed in reindeer populations this summer, may just be a worrying and sad taste of what is to come at higher latitudes, where warming has been much larger than the global average. Many of the tipping point effects we know about relate to the poles. The CCRA has a section on ‘climate surprises and missing processes’ such as rapid arctic ice melt and methane release from permafrost, but we know that these risks are overlooked in planning at the moment, and this needs to change.

Adaptation is not being resourced sufficiently

There has been a marked erosion of resourcing for adaptation in England since 2009. Following the publication of the 2009 UK Climate Projections, the Prime Minister asked sixteen departments to produce Departmental Adaptation Plans, which were published in 2010. These Plans contained a detailed assessment of the adaptation plans and policies of each department; something that has not been replicated in the subsequent two iterations of the National Adaptation Programme in 2013 and 2018. Government funding for adaptation support services in England – for the UK Climate Impacts Programme between 1997 and 2009, Climate Ready service between 2010 and 2017 and the nine Regional Climate Change Partnerships – has ended. Dozens of officials worked in the climate team in Defra, and with other departments to create the first NAP in 2013. This was still far fewer than the hundreds working on mitigation in the Department of Energy and Climate Change, but there was a definite upward trajectory. Only a handful of officials existed in the same team in 2018.  A team of this size cannot coordinate and support adaptation policy effectively across Government. A team of any size cannot put in place the policies needed without support and direction from Ministers and senior officials.

Adaptation should be a no-brainer. It is sustainable development.  It is going to be essential for meeting Government goals on health, biodiversity, and supporting the economy. Alongside efforts to reduce emissions, we should be seeing much greater uptake of measures like passive cooling in new and existing homes, urban greenspace including green sustainable drainage, property-level flood resilience; managed realignment of the coast; habitat restoration; monitoring of pests and disease risks; water efficiency; business continuity planning; and ongoing monitoring and data collection.

We have been saying the same simple message, over and over, for years, and will keep saying it long after the tumult of EU-exit has died down.


This article was originally published by the Committee on Climate Change read the original article here.
Cover photo by Jervis Sundays, Kenya Red Cross Society published on Creative Commons.
Meet Dr Xianfu Lu, Acclimatise’s new head of Analytics

Meet Dr Xianfu Lu, Acclimatise’s new head of Analytics

This month, Acclimatise has appointed Dr Xianfu Lu to lead its Analytics Division. Xianfu brings a wealth of experience working with the Asian Development Bank, UNDP and UNFCCC, applying the latest climate data to real-world decision-making frameworks. Xianfu will help to ensure that Acclimatise’s analytics services grow to meet the fast-growing demand for new tools and software that support climate resilient decisions. “I am exceedingly excited about joining Acclimatise,” Xianfu said, “the time has arrived for climate action: we now have the Paris Climate Agreement, we have the TCFD recommendations, and we have a corporate community and financial services sector ready to engage.”

Xianfu’s wide-ranging experience makes her ideally placed to ensure that Acclimatise continues to provide analytical tools that make climate data useful for its clients. Trained as an applied meteorologist, Xianfu has been working on climate risk assessment and management for over 20 years. She began her career as a research scientist developing and applying climate risk scenarios at the University of East Anglia and was a coordinating lead author for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.

Since then, Xianfu has been putting her technical expertise into practice. She has worked with the UNDP providing technical support to over 140 countries for their vulnerability and adaptation assessments and has worked at the UNFCCC secretariat including leading the support for negotiations on a number of issues related to climate resilience and adaptation within the Paris Climate Agreement. Most recently, Xianfu was the adaptation lead of the Asian Development Bank where she helped establish and operationalise the institution’s climate risk assessment and management framework.

“It’s very exciting to have Xianfu joining the company” said Acclimatise CEO John Firth, “we have ambitious plans for our Analytics business and Xianfu’s knowledge and experience makes her perfectly placed to ensure that our tools and software continue to lead the market.”

Xianfu’s experience at ADB included working with Acclimatise’s Aware for Projects™ tool which forms part of the physical climate risk screening process for ADB’s investments. Her experience institutionalising the climate risk framework gave her a clear appreciation of the challenge of developing tools that can be integrated into decision-making processes successfully. According to Xianfu, this remains the challenge for data analytics companies. “Although there has been a rapid growth in the offerings of data analytics including AI-enabled tools, truly user-friendly and technically robust analytics tools remain a rarity,” she said.

We have never known so much about the Earth’s climate system as we do today. The amount of scientific data and information about past, present and future climate is growing exponentially, as historic records are digitised, satellites provide earth observation data on a daily basis, and climate models become ever-more advanced. However, climate data alone is not sufficient to enable corporates, investors or governments to make better decisions and build climate resilience. “Since physical climate risk is a topic new to businesses and the financial services sector, external professional services are needed to identify, quantify, manage and disclose material risks and opportunities.” Explains Xianfu, “given the technical complexity of assessing and managing physical climate risk… analytics tools and software are needed.”

If done well, climate analytics software can help financial institutions and businesses to assess physical climate risks across their portfolios in line with TCFD recommendations and can facilitate climate-resilient investment decisions. “It is particularly important to highlight that analytics software must be user-friendly so that the task of assessing physical climate risks and opportunities is manageable and makes practical sense and, at the same time, is technically sound,” said Xianfu. “To achieve this, we need not only climate information based on state-of-the-art climate science but also a thorough understanding of the business processes and decision criteria of any given business or financial services industry.”

As well as driving forward the development of new analytics tools, Xianfu will help build on the successes of Acclimatise’s current range of climate tools and software. “With Xianfu on board, we will continue to refine and develop our existing commercial tools such as Aware™ which is used by four of the largest development banks to screen their investments for climate risk and identify investment opportunities, MiCA which enables the mining sector to access relevant climate data for any asset anywhere in the world, and our thresholds tool which combines climate data with asset thresholds to support corporates to understand climate risks to their facilities and operations.” said Bob Khosa, Technical Director of Acclimatise Analytics.

Xianfu is confident that Acclimatise’s fifteen-years of experience of integrating climate risks into decision-making processes through its advisory services can be increasingly leveraged in support of its analytics offerings. “With a most talented and dedicated team and unparalleled experience in delivering climate risk assessment and management services, Acclimatise cannot be a better home for me to apply my unique skill sets, to support the management of climate risks and opportunities for our clients, through which we can help to strengthen climate resilience of economies, communities and natural environments around the world.”


Podcast: Global law firm Clyde & Co. warns clients of a ‘wave of litigation’ from climate change

Podcast: Global law firm Clyde & Co. warns clients of a ‘wave of litigation’ from climate change

In this Acclimatise Conversation on Climate Change Adaptation, we speak with Clyde & Co lawyers Wynne Lawrence and Nigel Brook, about the emerging field of climate liability risk and the pioneering work that the firm is doing to advise its clients about how to respond.

In September 2015 the Governor of the Bank of England, Mark Carney, gave his seminal ‘Tragedy of the Horizon’s’ speech, to the insurance market at Lloyd’s of London. In it, he highlighted the severe threats posed by climate change to the financial system and warned the problem risked being ignored because of institutional near-sightedness.

“The classic problem in environmental economics is the ‘tragedy of the commons’… but climate change is a tragedy of the horizon,” Carney said, “We don’t need an army of actuaries to tell us that the catastrophic impacts of climate change will be felt beyond the traditional horizons of most actors. It will impose costs on future generations that the current one has little direct incentive to fix.”

The horizon for monetary policy goes out just a couple of years, and financial stability only about a decade. Carney went on to outline the three main ways in which climate change can affect financial stability:

  1. Physical risks like storms and floods;
  2. Transition risks associated with the transition to a low carbon economy; and
  3. Liability risks, legal claims by those suffering losses due to climate change.

Much of the attention since then has been on the first two categories, the physical and transition risks, but a growing number of lawyers and pioneering legal firms are drawing attention to the third category, the liability risks.

Their work has been reinforced by a growing number of international regulations and national laws and a growing body of case law. One such firm is Clyde & Co, a global firm that focusses on five key sectors: insurance, energy, trade and commodities, infrastructure and transport. The firm soon realised that climate change posed risks to all of these sectors, and so they set up a cross-disciplinary team on climate resilience. Listen to the full podcast to learn more.

Download Clyde & Co.’s climate resilience reports here.

Climate and law: Sarah Barker, Special Counsel and Head of Climate Risk Governance at MinterEllison

Climate and law: Sarah Barker, Special Counsel and Head of Climate Risk Governance at MinterEllison

Climate change is increasingly being understood as an issue of financial risk to corporates. This has brought the issue to the attention of corporate lawyers like Sarah Barker, Special Counsel and Head of Climate Risk Governance at MinterEllison, the largest commercial law firm in the Asia Pacific. For over six years, Sarah has been a leading voice in the field of climate risk governance for business. 

As climate change is now widely accepted as a financial risk issue, it necessarily enlivens established legal frameworks around corporate management and disclosure of climate risk. In this Acclimatise Conversation on Climate Change Adaptation, Sarah Barker talks us through why it is so important, from a legal perspective, for businesses to govern for the financial risks associated with climate change.


Cover photo by Dan Schiumarini on Unsplash.
Podcast: Legal implications of climate change are a big deal for corporates says legal analyst Marcela Scarpellini

Podcast: Legal implications of climate change are a big deal for corporates says legal analyst Marcela Scarpellini

Climate change and its impacts cause hundreds of billions of dollars of damage each year. As the scale of losses increases, so too will the number of legal cases apportioning blame to those most responsible. There have already been over one thousand litigation cases related to climate change, a number that is expected to rise dramatically as climate change continues, and legislation and regulations increase. However, there is another factor driving the number of legal cases: advances in climate science and the tools to interpret it.

When it comes to litigation, it is important to be able to identify some sort of loss, and also attribute that loss to the actions, or non-actions, of a legal entity. In the past it has been difficult to apportion blame for climate change impacts to individual companies or governments. It has also been difficult to argue that their failure to act to build resilience to climate change constitutes negligence that has led to a specific loss. However, as the science of climate change advances, a new suite of tools is changing all of this.

In this interview we speak with Marcella Scarpellini, a lawyer and legal analyst at right. based on science, a climate metrics and data services provider that is helping companies manage the financial risk of climate change. The company has developed its X-Degree Compatibility (“XDC”) tool, a science-based climate metric that estimates how many °C the Earth would warm by 2050 if all companies were to operate as emissions-intensively as the company under consideration.

The XDC tool can be used by companies, investors, governments or others who want to better understand their contribution to climate change, and gauge how to best respond. It is also useful for lawyers to hold companies and governments to account, showing whether they are contributing to a wold of 1.5˚C and in line with the Paris Agreement or a much hotter world where climate damages will be significantly higher.

“For corporates [climate change] is going to be big” Marcella said “As climate change increases the search for culprits is also going to increase… we know that there is causality between emissions and climate change, so people are going to start pointing fingers. I think for companies it will be in the forms of fines and penalties, of course litigation, and even class action damages are expected.”


Cover photo of Hurricane Katrina Damage / From Wikimedia Commons
How can the biodiversity and climate crises be tackled together?

How can the biodiversity and climate crises be tackled together?

By Natalie Sauer

Ecologists have long conceived of the earth as a living organism where every plant, animal, river and cloud are interconnected.

In the political sphere, however, the climate and biodiversity crises have more often than not remained solidly bunkered away from each other. That could be changing.

A series of major meetings are pushing the governments of the world to address both crises as one. Experts hope they could lead to a major shift in the way we think about tackling climate change.

On Monday, a new blockbuster report revealed that up to one out of eight million known plant and animal species could be at risk of extinction.

Global warming is the third biggest factor driving species extinction after changes in land and sea use and the direct exploitation of organisms, according to the report by the UN’s biodiversity science body IPBES. A hike in temperature of just 1C has impacted life from the level of ecosystems to that of genetics. At 1.5C to 2C of warming – the goals of the Paris climate agreement – the report warns the ranges of most of the world’s species on land will shrink significantly.

But this relationship, as scientists and politicians increasingly note, isn’t only negative: often – though not always – conservation efforts bolster the climate too. Healthy ecosystems are imperative for the earth’s capacity to mop up C02.

“We know that ecosystems are currently absorbing 25% of emissions. Another 25% of our emissions are going into the oceans, which is causing ocean acidification,” Guy Midgley, a coordinating lead author of the report, said on Monday. “Together, that’s half of our emissions not ending in the atmosphere because of the health of our ecosystems.”

Though some ecosystems act as better sponges than others. Coastal habitats, such as mangroves, sea grass and salt marshes can soak up carbon up to 40 times faster than tropical forests. Peatlands, which cover 3% of the land surface, represent the largest terrestrial carbon store.

Meanwhile, evidence of the critical role of certain animals in the maintenance of these ecosystems continues to stack up. Known in zoology as cornerstone species, the beaver is vital to wetlands through dam construction, the scaly pangolin protects forests from termite ravages, while by stomping vegetation, African forest elephants encourage the growth of larger trees capable of absorbing more carbon.

It is estimated that so-called ‘nature-based solutions’, which benefit climate and biodiversity, could provide 40% of the carbon emissions cuts needed by 2030 to give a decent chance of limiting warming below 2C. Yet they receive less than 3% of climate funding.

Conservationists familiar with diplomatic negotiations on biodiversity and climate change complain of bureaucratic ghettos. The two UN programmes, the Convention on Biodiversity (CBD) and UN Framework Convention on Climate Change (UNFCCC), don’t really talk to each other, Beatriz Luraschi, a researcher on climate change and biodiversity at the UK nature charity RSPB, told Climate Home News.

While “the CBD has always been more inclusive of other issues, including climate change,” Luraschi said, citing a decision passed at the CBD in 2018 in Egypt calling on states to slash emissions through ecosystems, “the same level of interest in biodiversity has never been reflected in the same formal setting in the UNFCCC. Even though there is some language in the Paris Agreement on maintaining environmental integrity, it just isn’t as explicit.”

This is changing. Frances Seymour, a senior fellow at the World Resources Institute (WRI), notes that there is growing appetite within the UN for literature on the crossovers, with a major report by the think tank due to be released in September.C

“It’s great that people are connecting the dots,” Seymour told CHN.  Forest and land emissions have long been a “stepchild in the broader climate world”, she said, which has focused on energy and other fossil fuel sources. The proximity of the IPBS report to a recent major release from the UN’s climate science panel has helped focus attention on the crossover.

The momentum to bring the two issues together is set to pick up at a flurry of critical gatherings in the next 18 months. UN chief Antonio Guterres will be calling on governments to present plans to slash emissions at a climate action summit in September. In December, climate talks in Chile are expected to focus on the importance of ocean health.

In autumn 2020, China will host a landmark summit on biodiversity in Kunming. The meeting is set to define new biodiversity targets, with expectations running high after governments failed to meet goals (2011-2020) formulated during the CBD in Aichi, Japan in 2010. Many hope this to be biodiversity’s Paris moment.

“People can’t help but see them as milestones in one roadmap towards either disaster or redemption,” Seymour said.

Overall, diplomatic initiatives aimed at tackling both crises are on the rise. With the meeting of G7 environment ministers coinciding with the publication of the IPBS report, heads of state issued the Metz Charter on Biodiversity. The non-binding document called on the group to recognise the vital role of biodiversity in contributing to climate regulation and helping communities combat natural disasters.  The group also committed to deploy “nature-based solutions… which can also enhance climate change mitigation and ecosystem restoration.”

Meanwhile, China (alongside New Zealand) is heading a UN working group on nature-based solutions, in the run-up to September’s climate action summit in New York. The aim is to encourage states to incorporate nature-based solutions in their climate pledges to the Paris Agreement.

Seymour hopes governments will put their money where their mouths are. “We haven’t seen a shift yet in financial resources… We’re off by an order of magnitude,” Seymour said. If countries update their climate commitments to include serious efforts on nature it “will really embody whether we’re serious about this or not”.

But this effort is not without obstacles, Li Shuo at Greenpeace China told CHN. “I think one challenge that this track faces is that the topic of nature-based solutions was sort of overlooked by the climate community. There wasn’t much diplomatic groundwork done on this issue.”

With land-use, agriculture and nature-related sectors contributing less than 10% of Chinese emissions, “energy and transportation-related issues are traditionally perceived as our climate issue”, Li said. “It’s a new learning process for government officials who are chairing this track.”

“The challenge for China is twofold: it has to start the action domestically. In the context of the the UN Climate Action Summit, China’s job is about inspiring the entire membership of the UN on this particular topic,” Li said.

When it comes to biodiversity, China and France are developing their own visions of leadership. The Chinese government is “now paying very close attention to the negotiations” leading to next year’s CBD meeting, with “the entire bureaucracy mobilised to deliver a good outcome”, Li told CHN.

But France, the host of the Paris Agreement, is pursuing a grander vision – a new overarching global treaty for nature. Back in 2017, Emmanuel Macron floated the idea of a treaty that would aid cooperation on environmental blights, such as plastics, but also the biodiversity and climate crises.

Next year, the port city of Marseille is set to host the World Conservation Congress. President of International Union for Conservation of Nature Zhang Xinsheng described the event as “central in mobilising the international community ahead of critical decisions to be taken later that year regarding global efforts to tackle biodiversity loss and climate change”.


Cover photo by Johnny Chen on Unsplash.
This article originally appeared on Climate Home News.
Video: Our changing fisheries: voices from Montserrat

Video: Our changing fisheries: voices from Montserrat

By Acclimatise News

A new video, “Our Changing Fisheries: Voices from Montserrat”, shines a light on the climate challenges being faced by Island nations’ fishing industries. The video, created by the Caribbean Natural Resources Institute (CANARI), highlights climate change impacts highlighted include rough seas, changing currents and more extreme hurricanes and storms that affect ability to fish and cause damage to fishing grounds and gear.

The video features local voices and perspectives from fisherfolk and other coastal and marine resource users on changes being experienced in Montserrat’s fisheries sector in the context of climate change, and ideas for building their resilience.

The video was developed as part of the Darwin Plus project, Climate change adaptation in the fisheries of Anguilla and Montserrat. This project is being implemented by CANARI in partnership with the Fisheries and Ocean Resources Unit – Montserrat, Department of Fisheries and Marine Resources – Anguilla and the Centre for Resource Management and Environmental Studies (CERMES) – University of the West Indies.

CANARI and the Fisheries and Ocean Resources Unit – Montserrat are continuing to work with the Montserrat fisherfolk and other coastal and marine stakeholders to disseminate the video and enable knowledge exchange to adapt and build resilient fisheries and related livelihoods.


Cover photo by Zhan Zhang on Unsplash.
Climate poses direct risk to real estate investment says ULI report

Climate poses direct risk to real estate investment says ULI report

By Will Bugler

The known and growing risks posed by climate change to large-fixed asset investments, has done little to put off some lenders from financing real-estate in some of the world’s most vulnerable areas. Such actions are coming under increasing scrutiny, with many investors and forecasters calling them ‘insane’. In a recent report, the Urban Land Institute and real-estate investment management firm Heitman assess the potential impacts of climate change on real estate assets and give some direction as to what investment managers and institutional investors might do to understand and reduce their climate risk exposure.

The report shows that while although many assets held by real estate investors are in cities vulnerable to the effects of climate change, most still rely on insurance to guide their risk decisions. However, as premiums are based on historical events, they are not a robust guide to climate change risk to investments. The report shows that physical risks from catastrophic events and chronic climate risk from slower changes to weather patterns, pose direct risk to real estate investments.

Derived from a series of interviews with leading institutional investors, investment managers, investment consultants and others, the report also shows that a growing group of investors and investment managers are exploring new approaches to find better tools and common standards to help the industry get better at pricing in climate risk in the future. These include:

  • Mapping physical risk for current portfolios and potential acquisitions;
  • Incorporating climate risk into due diligence and other investment decision-making processes;
  • Incorporating additional physical adaptation and mitigation measures for assets at risk;
  • Exploring a variety of strategies to mitigate risk, including portfolio diversification and investing directly in the mitigation measures for specific assets; and
  • Engaging with policymakers on city-level resilience strategies, and supporting the investment by cities in mitigating the risk of all assets under their jurisdiction.

Such tools and methods are becoming necessary to reassure institutional investors and other lenders that their investments are secure. The report points to a series of resources, standards and guidelines that form part of a rapidly developing toolkit that can be used to better understand and manage climate risk.

It is becoming increasingly likely that investors will be expected, and indeed required, to ensure appropriate risk management measures are in place to protect investments from climate risk exposure, and to encourage more robust practices in real-estate construction and development.

A copy of the ULI report “Climate risk and real estate investment decision-making” can be found here.


Cover photo by Chuttersnap on Unsplash.
CIF and GDI host first joint learning event

CIF and GDI host first joint learning event

By Acclimatise News

On June 6th and 7th The Climate Investment Funds (CIF) and Global Delivery Initiative (GDI) will host a two-day learning event at World Bank headquarters aimed at sharing lessons from their findings across Latin America, Asia and Africa. Acclimatise’s Virginie Fayolle will be a part of a panel speaking on how to rapidly drive private sector investment in climate adaptation in developing countries.

In 2017, CIF and GDI joined forces to better understand the operational challenges that constrain climate finance projects. The collaboration led to the development of six delivery cases, each mapping how practitioners working on climate finance projects are embedding adaptive management to address questions such as:

  • What are the inherent risks of private climate financing, and what instruments make projects bankable?
  • How do governments manage competing interests in climate-smart regulatory reform?
  • What beneficiary-selection strategies are most effective for managing collective action problems and maximizing welfare outcomes?

The cohort of speakers draws from diverse institutional perspectives – multilateral development banks, bilateral organisations, governments, the private sector, and civil society – thereby creating a well-rounded discourse that aids practitioners to deliver ground-breaking projects within challenging contexts.

Click here to register for the event.


Cover photo by Daniele Levis Pelusi on Unsplash.
‘Powerful evidence’ of global warming’s effect on seasons found in troposphere

‘Powerful evidence’ of global warming’s effect on seasons found in troposphere

By Daisy Dunne

Scientists studying the troposphere – the lowest level of the atmosphere – have found “powerful evidence” that climate change is altering seasonal temperatures.

A study published in Science finds that climate change has caused an increase in the difference between summer and winter temperatures across North America and Eurasia over the past four decades.

This could be the result of summer temperatures warming at a faster rate than winter temperatures in these parts of the world, the lead author tells Carbon Brief.

The findings show the “substantial human influence on Earth’s climate, affecting not only global averages, but also local and seasonal changes”, another scientist says.

Most of the world’s weather originates in the troposphere, a second scientist tells Carbon Brief, meaning that changes to seasonal temperatures could be affecting the likelihood of extreme weather events, such as flooding and drought.

Sky high

Evidence shows that the seasons are changing. In Europe, for example, analysis of the first-emergence dates of more than 500 plant species shows that the first day of spring has advanced by six to eight days in the past three decades.

Moon with orange-coloured troposphere band, the lowest and most dense portion of the Earth's atmosphere. The troposphere ends abruptly at the tropopause, which appears in the image as the sharp boundary between the orange - and blue - coloured atmosphere. Credit: NASA Photo / Alamy Stock Photo. D7KRFX
Moon with orange-coloured troposphere band, the lowest and most dense portion of the Earth’s atmosphere. The troposphere ends abruptly at the tropopause, which appears in the image as the sharp boundary between the orange – and blue – coloured atmosphere. Credit: NASA Photo / Alamy Stock Photo.

However, working out to what extent seasonal changes can be explained by climate change – rather than natural climate variability, caused by phenomena such as El Niño– presents more of a challenge.

To quantify the influence of climate change versus natural variability, scientists often carry out “attribution” studies.

The new study is the first to assess how climate change could be influencing seasonal temperature changes in the troposphere – a layer that covers roughly the first 17km of the atmosphere above the Earth.

Writing in their research paper, the team, led by Dr Ben Santer, a scientist at the Lawrence Livermore National Laboratory, says:

“Our results suggest that attribution studies with the changing seasonal cycle provide powerful evidence for a significant human effect on Earth’s climate.”

Satellite sentinels

For the study, the researchers analysed atmospheric temperature data recorded by satellites throughout the summer and winter months from 1979-2016. (Carbon Briefhas published an explainer on how satellite temperature records compare with measurements at the Earth’s surface.)

The map below shows how the difference between summer and winter temperatures, expressed as an average per decade, has changed across the world.

On the map, dark red indicates where the difference between summer and winter temperatures have grown larger, while dark blue shows where the difference has grown smaller.

Temperature difference between summer and winter months (per decade) from 1979-2016. Red shows a large temperature difference between the seasons, while blue shows a small temperature difference.
Temperature difference between summer and winter months (per decade) from 1979-2016. Red shows a large temperature difference between the seasons, while blue shows a small temperature difference. Source: Randel (2018) Data source: Santer et al. (2018)

The map shows that the difference between summer and winter temperatures has increased the most in mid-latitude regions, particularly in the northern hemisphere.

This is because, in these regions, atmospheric summer temperatures are increasing at a faster rate than winter temperatures – causing the disparity between the two seasons to grow larger and larger, the researchers say.

The northern hemisphere has experienced more summertime warming than the southern hemisphere because it contains more land, the researchers say. The presence of land means that less heat can be absorbed by the ocean – leading to amplified atmospheric warming, says Santer and co-author Stephen Po-Chedley, a fellow at Lawrence Livermore National Laboratory. In a joint statement, the researchers tell Carbon Brief:

“Countries with the largest observed changes include Mongolia and eastern Russia. Parts of the northeast and western US and eastern Europe have also seen substantial increases in the tropospheric seasonal cycle. Changes tend to be small over the UK.”

The map also indicates that the eastern edges of both North America and Eurasia have experienced the greatest amounts of warming. This could be because, during the winter in these regions, warm air masses are carried from east to west – leading to milder winters along western continental margins, the researchers say.

Changes in temperatures are not as pronounced around the tropics because this region is not highly seasonal, the researchers say. Instead, the seasons in tropical regions are typically defined by rainfall (“wet” and “dry”, for example), rather than by temperature.

In contrast, the difference between summer and winter temperatures around the poles has shrunk over the past four decades, the map shows. In these regions, winter temperatures are rising faster than summer temperatures, the research finds.

In the Arctic, this winter warming is partly influenced by the diminishing presence of sea ice during summer months, the researchers say. With less sea ice present, the ocean absorbs more heat – which is later released during the winter, the researchers say.

The reason that winter atmospheric warming may have accelerated above Antarctica is less clear. However, previous research suggests that the presence of polar clouds in the stratosphere (which sits above the troposphere) could be playing a role.

‘Substantial human influence’

To understand to what extent the observed seasonal changes were influenced by human-caused climate change, the researchers compared the satellite results to climate models.

The model simulations, which ran from 1979-2016, included a range of natural factors that can influence tropospheric temperature, including the cooling effect of volcanic eruptions and aerosols. To include the impact of human-caused climate change, the researchers used a “business-as-usual” emissions scenario known as RCP8.5.

The results show that only simulations that include the impact of human-caused climate change could correctly predict the patterns of seasonal temperature change recorded by the satellites. The researchers say:

“The real-world observations are much closer to model simulations that include increases in greenhouse gas concentrations, allowing us to attribute the observational record to human influence using formal climate detection and attribution techniques.”

The results indicate that humans are having a “substantial influence” on the temperatures in the troposphere, says Dr William Randel, a senior scientist at the National Center for Atmospheric Research, who was not involved in the research. In an accompanying perspectives article, he writes:

“[The] findings provide further markers of a substantial human influence on Earth’s climate, affecting not only global averages, but also local and seasonal changes.”

Weather worries

However, it is not clear how temperature changes in the troposphere could affect conditions at the land surface, he adds:

“The connection between changes at the surface and the free troposphere awaits explanation.”

One possible effect could be changes to the timing and likelihood of extreme weather events, says Prof Neil Harris, from the Centre for Environment and Agricultural Informatics at Cranfield University, who was not involved in the research. He tells Carbon Brief:

“The paper significantly increases confidence that the observed changes in the troposphere – where all our weather is – are consistent with models and that they are of human origin. This gives more confidence in the existing findings of an increase frequency of extreme weather, such as more intense rainfall and more extreme summer hot spells.”


This article was originally published on The Carbon Brief.
Cover photo by Alexander Popov on Unsplash.