The Real Top Story – Part 2 of Royal Society 2017 Climate Update

INTRODUCTION

In our last issue, OregonPEN printed the first part of an adaptation of a telling report by Royal Society, its November 27, 2017 Climate change update report (available at royalsociety.org/climate-change).

In the report titled, Climate Update: What have we learned since the IPCC’s 5th Assessment Report?, the scientists at the Royal Society examined data that has been collected since the 2013 and 2014 5th annual assessment (AR5) by the Intergovernmental Panel on Climate Change (IPCC) of the evidence about climate change and its impacts.

Each “Question” of this report can be read and understood individually, but Royal Society has crafted the whole as a broad thematic progression, with the inclusion of new studies that will clarify understanding over time. As the original introduction states, “In some cases, new work suggests changes in the probability of certain outcomes occurring, but in most cases the broad statements made by IPCC still appear valid.”

With the next IPCC assessment report (AR6) not due until 2022, while the pace of palpable effects appears to be quickening, reports such as the Royal Society’s update lets us assess whether the evidence presented since the publication of AR5 affects the assessments made then.

The last OregonPEN presented the first eight sections from the Royal Society update, including such fundamental questions as

  • How sensitive is global temperature to increasing greenhouse gases?
  • How are methane concentrations changing and what does this mean for the climate?
  • Was there a ‘pause’ in global warming?

In this issue, OregonPEN proudly provides the rest of the text from this important survey of where we are, and where our fossil fuel emissions are taking us:

  • Question 8 Is the land taking up carbon dioxide because of faster plant growth?
  • Question 9 How do increasing carbon dioxide concentrations impact ocean life and fisheries?
  • Question 10 How will climate change affect food production on land?
  • Question 11 What is the influence of climate change on water availability across the globe?
  • Question 12 What is the influence of climate change on species extinction?
  • Question 13 How will human health be affected by climate change

An Appendix follows

Adapted from Royal Society’s November 27, 2017 Climate change update report; original viewable at royalsociety.org/climate-change.

Abbreviations used throughout this report:
IPCC Intergovernmental Panel on Climate Change
AR4/AR5/AR6 Fourth/Fifth/Sixth Assessment Report of the IPCC
RPC Representative Concentration Pathway

QUESTION EIGHT – Is the land taking up carbon dioxide because of faster plant growth?

Summary

Increasing atmospheric carbon dioxide increases plant growth, in turn removing carbon dioxide from the atmosphere, but this increased removal is counteracted by the challenge of continued climate change for terrestrial ecosystems.

In AR5 IPCC said:

With high confidence, the carbon dioxide fertilisation effect will lead to enhanced NPP [net primary production], but significant uncertainties remain on the magnitude of this effect, given the lack of experiments outside of temperate climates.

What is this about?

Plants use the energy of sunlight to convert carbon dioxide into sugars, through photosynthesis. The total amount of carbon taken up by an area of land each year is gross primary production. About half of this carbon is used to create new plant material, called net primary production, the other half being released to the atmosphere by plant respiration.

Plant material eventually decays with most of the dead carbon being consumed or broken down by fungi, bacteria, animals or by fire, and carbon being released back to the atmosphere as a result. The net carbon balance of an ecosystem is the balance between these processes of carbon uptake and release.

Increasing atmospheric carbon dioxide concentration increases photosynthesis and reduces transpiration, generally leading to increased plant growth and water use efficiency. The processes of plant death and carbon release lag behind, resulting in net carbon uptake by the ecosystem. According to terrestrial ecosystem models, this ‘carbon dioxide fertilisation’ is the main cause of the net uptake of carbon dioxide emissions by the land (the land carbon sink).

It is also thought to be the main cause of the observed increase in vegetation leaf cover (the ‘greening’ of the biosphere) as more carbon is being allocated to leaves.

What was the basis for the statement in AR5?

IPCC concluded that co2 “fertilization” leads to enhanced primary production, with net primary production increasing by 20 to 25% for a doubling of carbon dioxide over pre- industrial levels.

However, nitrogen and phosphorus availability were considered very likely to limit that increase, with nitrogen limitation prevalent in temperate and boreal ecosystems and phosphorus limitation in the tropics.

What do we know now?

Global observations
Several lines of evidence point to an increase in primary production over the industrial period. Observed changes in global atmospheric co2 and oxygen concentrations indicate, with a high degree of confidence, that the terrestrial biosphere is absorbing about one third of anthrpogenic co2 emissions, thereby acting as a brake on the rate of atmospheric co2 increase.

Satellite observations of vegetation cover show widespread “greening”. Models suggest that this greening is predominantly due to co2 fertilisation because of increased water-use efficiency as atmospheric co2 rises, although climate and land use change have also contributed. The large increase observed in the amplitude of the atmospheric carbon dioxide seasonal cycle (especially at high latitudes) has been predominantly caused by increasing photosynthesis, as a response to co2 fertilisation (and potentially also climate change at high latitudes). Independent atmospheric observations of carbonyl sulphide – which is taken up with co2 during photosynthesis, but not released again – indicate that gross primary production increased by circa 30% during the 20th century. Long-term field inventories also support a long-term carbon sink in the world’s forests.

Global models

In AR5 only two of the Earth System models used included a coupled carbon-nitrogen cycle which accounted for nitrogen availability effects. Both models used the same land model, which showed greatly reduced co2 and a greatly reduced climate- carbon cycle feedback. Although carbon-only models are expected to overestimate land carbon sinks, recent analyses have shown that the extremely low responses found with the two carbon-nitrogen models in AR5 are probably unrealistic.

Limits to carbon dioxide fertilisation

Current understanding shows that reality is more complex than was indicated in AR5. In some ecosystems the effect of co2 on plant growth is independent of nitrogen availability; other ecosystems have shown little or no co2 effect under low nitrogen availability. Much less is known about the influence of phosphorus availability, which may be particularly constraining in tropical ecosystems.

First experimental results from a forest experiencing phosphorus limitation have suggested no response of plant growth to increasing co2, but there are still no experiments in mature tropical forests. Another factor that may limit co2 fertilisation is forest demography, with tree mortality accelerating as a result of enhanced tree growth.

Fertilisation versus climate feedbacks

The positive effect of increasing co2 on the land carbon cycle currently dominates over the negative effect of climate change (primarily the warming induced increase in soil carbon decomposition rate).

Further climate change will affect this balance and reduce land carbon sinks efficiency, with regional droughts reducing productivity and higher temperatures accelerating rates of decomposition.

Conversely, between 2002 and 2014 the growth rate of atmospheric co2 stayed relatively constant despite a continued increased of anthropogenic emissions, indicating an increase in the size of carbon sinks. Recent studies suggest that the reduced level of surface warming in that period led to a slowdown in temperature-driven ecosystem respiration. How long land carbon dioxide uptake will continue to dominate over release is unknown.

How might this affect the IPCC statement?

The statement in AR5 remains true. Increasing atmospheric carbon dioxide continues to increase net primary production and so leads to a proportion of that extra carbon dioxide being removed from the atmosphere. However, there are still large uncertainties about the geographic distribution, and the future, of the land carbon sink. The benefit of increased plant growth (including of crops, which are discussed later) will be reduced if rising temperatures and change in precipitation cause heat stress or water stress and reduce plant productivity.

 

QUESTION NINE – How do increasing carbon dioxide concentrations impact ocean life and fisheries?

Summary

Carbon dioxide emissions are redulting in warming, deoxygenation and acidification of the ocean and this poses significant risk to ocean ecosystems including those relied on for food and livelihoods.

In AR5 IPCC said:

Marine organisms will face progressively lower oxygen levels and high rates and magnitudes of ocean acidification, with associated risks exacerbated by rising ocean temperature extremes.

Climate change adds to the threats of over-fishing and other non-climatic stressors.

What is this about?

The ocean plays a key role in regulating climate. It has absorbed about 25% of anthropogenic carbon dioxide emissions since 1750. This has had the effect of causing the oceans to become more acidic. The ocean has also absorbed about 90% of Earth’s additional heat since the 1970s, but this has led to ocean warming and decreasing oxygen content (due to reduced oxygen solubility caused by warming and decreased supply to the ocean interior due to less mixing).

These changes have important consequences not only for marine biodiversity and ecosystems but also for the goods and services they provide, including protein and other nutrients from fin fish and shellfish, coastal protection, and livelihoods for hundreds of millions of people. The ocean’s content of carbon, oxygen, acidity and heat would continue to change long after atmospheric carbon dioxide emissions cease, as the changes only spread slowly into deeper waters, but the extent and rate of carbon dioxide emissions will affect the magnitude of the changes.

What was the basis for the statement in AR5?

AR5 concluded that increasing carbon dioxide and temperature will cause changes in global marine species’ distributions and reduction of marine biodiversity in sensitive regions. Evidence for these changes came from model projections of ocean warming and acidification under different emission scenarios, numerous laboratory and field studies, and meta-analyses.

Whilst global ocean warming is expected to cause the number of species and fisheries catch potential to increase (on average) at mid and high latitudes, decreases are projected in the tropics and in semi-enclosed seas. IPCC also assessed that progressive expansion of ocean minimum zones and anoxic ‘dead zones’ will further constrain fish habitats. Such changes would challenge the sustained productivity of fisheries and the provision of other ecosystem services, especially in tropical regions.

What do we know now?

Many new studies have further documented effects attributed to acidification. It also appears that deoxygenation is happening faster than was projected by models. Effects, including coral bleaching, have been attributed to warming which continues to occur in all oceans. There have been new studies on the complex effects of multiple stressors on biodiversity, ecosystems and fisheries.

Other studies have shown that local variability in conditions and the response of different species can result in complex food-web interactions. There is potential for a shift or reduction in the ranges of some species, or even loss of some ecosystems, such as those supported by corals, with reduced functioning of the food web. Whilst some species may be able to acclimate, many will not.

There is increasing evidence that a high emissions scenario will significantly alter many ecosystems and food webs through increased warming, acidification and deoxygenation and the spread of oxygen minimum zones or their combination. Not all of the impacts would necessarily be negative but these stressors can threaten fin fisheries and shellfish aquaculture in vulnerable regions.

A low emissions scenario reduces the overall risk, but even in this case the risk to current coral reef ecosystems, for example, remains high. The potential loss of tropical coral reefs would not just reduce local biodiversity but would also have major consequences for coastal protection, tourism, income, livelihoods
and fisheries.

The nutrition (protein and micro-nutrient supply) of about 1.4 billion people is at risk as fish make up a significant proportion of their animal-based food. Climate change under a high emission scenario is projected to reduce fish catch by about 5% globally and 30% in tropical regions. The communities that live there are the most vulnerable, due to their dependency on wild fish, their poor current adaptive capacity, and projected increases in food demand (related to population growth).

How might this affect the IPCC statement?

On this basis we expect the IPCC statements to stand. Climate change will place multiple stresses on many marine organisms, potentially resulting in decreases of biodiversity, changes to species distribution and altering marine food webs and ecosystems.

The evidence base is now stronger and more complex and diverse. The combined impacts of warming, deoxygenation and acidification on marine ecosystems and fisheries may lead to a more adverse risk assessment, but studying and attributing their combined impacts is difficult.

QUESTION TEN – How will climate change affect food production on land?

Summary

Increasing carbon dioxide can increase crop yields while high temperature and drought in some regions can decrease them. The aggregate impact at the global level is for climate change above 2 degrees Celsius to reduce yields.

In AR5 IPCC said:

For wheat, rice, and maize in tropical and temperate regions, climate change without adaptation is projected to negatively impact production for local temperature increases of 2°C or more above late-20th-century levels, although individual locations may benefit.

What is this about?

Wheat, rice and maize are staple crops and feeding the growing human population depends on their continued success. Climate change poses a range of effects: the increased concentration of carbon dioxide can increase crop yields, while changes in temperature and rainfall will have a variety of effects, with very high temperatures and drought both adversely affecting yield.

Taking all factors into account, AR5 concluded that a change of 2°C or more above late-20th-century levels will adversely affect yields and food production.

What was the basis for the statement in AR5?

The statements were based on a global analysis of studies up to 2013 reporting climate impacts on crop yields. While climate change impacts were variable across crop types and by region, the global impacts on food production for these crops were negative.

What do we know now?

Some studies since 2013 project somewhat lower impacts than those estimated in the analysis on which the IPCC statement is based, and more regional nuance has emerged, with some regions expected to see increasing yields for some crops. The conclusions in the original statement are not altered (see figure), though new studies point strongly to the importance of accounting for how land use and cropping intensity might change.

Since 2013, there has been more emphasis on nutrition, and not only on yield change. Higher-yielding wheat crops adapted to higher temperatures, or growing under increased atmospheric carbon dioxide concentrations, may produce grain of poorer nutritional quality under climate change.

AR5 considered productivity changes in yields for the three major cereals, but since 2013, we can also say more about the impact of climate change on other crops and rangelands (open lands used for grazing).

Subsequent analyses have examined potential changes in food production as a result of changes in the area suitable for agriculture, though greater confidence in the conclusions of such studies requires the further inclusion of other criteria for crop growth and development, soil nutrient availability and the incorporation of uncertainty and sensitivity analyses. Rangelands will be impacted by climate change, but this may not necessarily translate to large impacts in animal production because of the capacity to intensify livestock production through production systems transitions, dietary supplementation and other means.

The need for transformative adaptation in agriculture might be large, and different depending on the climate scenario and socio-technical development pathways. Since 2013, the costs of adaptation for agriculture have been estimated at 3% of total agricultural production costs in 2045 ($145 billion), somewhat higher than reflected in the literature available in 2013.

Since grass yields are less affected by climate change than arable crop yields, production system shifts towards mixed livestock-cropping systems appear to be a cost effective adaptation option.

How might this affect the IPCC statement?

On this basis we expect the conclusions to stand, though the evidence base is now stronger and more nuanced.

 

QUESTION ELEVEN – What is the influence of climate change on water availability across the globe?

Summary

Climate change will lead to reductions in water resources in many water-stressed regions, particularly in the dry subtropics, but the changes will vary between regions and there remains considerable uncertainty in the magnitude of change.

In AR5 IPCC said:

Freshwater-related risks of climate change increase significantly with increasing greenhouse gas concentrations.

Climate change over the 21st century is projected to reduce renewable surface water and groundwater resources significantly in most dry subtropical regions, intensifying competition for water among sectors.

What is this about?

The availability and reliability of water supplies have a major influence on societies and economies. Where resources are limited or unreliable, societies have tended to develop infrastructure and institutional arrangements to reduce risks. Areas with limited or unreliable resources are found in dry subtropical regions, but resources can also be placed under pressure where demands are high. Future river flows and groundwater recharge will be affected by climate change, and impacts vary between catchments. Globally, changes are predominantly determined by changes in precipitation and at this global scale, wet regions are projected generally to get wetter, and dry regions to get drier. Increases in evaporation exaggerate the effects of reductions in precipitation and can offset small increases. In some places (for example downstream of parts of the Himalayas) future river flows will be affected by changes in the volume of meltwater from glaciers.

Future water availability and reliability are also affected by other changes in the catchment (such as land use change) and by changes in demands for water resources. These depend on future population change and patterns of exploitation of water resources. At the local scale, these other drivers may be more significant for future reliability of water supply than climate change.

What was the basis for the statement in AR5?

The AR5 conclusions were based on a small number of global-scale assessments of change in river flows and recharge, a larger number of local-scale studies and on changes in runoff as simulated by climate models.

What do we know now?

The strong relationship between changes in precipitation and changes in river runoff has been confirmed by more global and local-scale studies. Projected reductions in runoff and groundwater resources are large in dry subtropical regions. Research using the current generation of climate models has shown that the ‘wet gets wetter and dry gets drier’ paradigm does not necessarily hold at the local scale and in all seasons.

Studies published since the AR5 have used multiple hydrological models as well as scenarios constructed from an ensemble of climate models to estimate hydrological changes. This wider range of evidence has resulted in larger assessed uncertainty ranges. Differences between hydrological models’ representation of evaporation and, to a lesser extent, processes during the cold season (the simulation of snow cover and the effect of soil freezing and thawing on runoff generation) have been shown to result in different magnitudes of response to the same change in climate.

A small number of studies have shown that vegetation changes stimulated by increasing carbon dioxide can influence the water cycle at the catchment scale. The effects vary with catchment vegetation and current climate (specifically whether the amount of evaporation that occurs is limited by the amount of water available rather than the energy available), but there is increasing evidence that the effects of carbon dioxide may be substantial in forested catchments and also in semi-arid environments where increased carbon dioxide leads to increased vegetation cover and therefore greater evaporation and less runoff or recharge. The effect at the regional and global scale is currently uncertain.

How might this affect the IPCC statement?

The IPCC statement was very qualitative and remains valid. Climate change is still projected to lead to reductions in water resources in many regions, particularly in the dry subtropics.

 

QUESTION TWELVE – What is the influence of climate change on species extinction?

Summary

Extinction rates are expected to rise, particularly at higher rates of climate change, and most seriously for those species unable to adapt in response.

In AR5 IPCC said:

A large fraction of both terrestrial and freshwater species faces increased extinction risk under projected climate change during and beyond the 21st century, especially as climate change interacts with other stressors, such as habitat modification, overexploitation, pollution, and invasive species.

What is this about?

Species depend upon local climates for suitable conditions, in a predictable seasonal cycle. Both conditions, such as food and pollinators, and abiotic conditions, such as water and shelter, can be disrupted by climate change. This can in turn cause alterations to the abundance and distribution of species, and lead to local extinctions and/or geographical range shifts.

The consequences will be more serious if new climate conditions cause species to go extinct globally or if resulting changes to biological communities have effects on key ecosystem functions including, for example, the carbon cycle.

What was the basis for the statement in AR5?

There was high confidence that species extinction rates would increase with the magnitude and rate of climate change, but low confidence in the fraction of species at increased risk, the regional and taxonomic focus, and the time frame over which extinctions could occur. Different mechanisms by which species might adapt to climate change, including dispersal, behavioural, genetic and evolutionary plasticity were all noted as significant but poorly understood.
What do we know now?

A synthesis of 131 species extinction studies concluded that 1 in 6 (16%) species might go extinct under high emission pathways compared to less than 3% under current levels of warming. This reduces to 1 in 20 (5.2%) under the international policy target of 2°C (see Figure); but with considerable variation depending on geographical region, type of species, and model assumptions. When global biodiversity was modelled under alternative socioeconomic growth pathways, mean species abundance was found to decline by 18 – 35% and extinction risk to increase for 8 – 23% of species under the high emissions pathway.

Local extinctions have been shown to vary spatially as well as with the extent of climate change: in marine areas local extinctions are expected to be concentrated near the equator and local invasions to be more common in temperate regions.

All these estimates have high uncertainty because many other biotic and abiotic factors determine species persistence and interact with climate changes. A common mismatch in spatial scale between climate models and species biology means models may have particularly poor predictive power for small-bodied and small-range species, which is especially significant given recent evidence of the important role of microclimates in providing refuges.

Species vary widely in their responses to climate changes. Empirical studies have identified certain demographic, ecological and genetic factors that explain variation in species vulnerability, as well as significant interactions between these, and with other stressors. Those species with poor dispersal ability, small ranges, facing physical barriers, with ecological specialisations and without a resting or dormancy period have been shown to be especially vulnerable.

The capacity for adaptation and the limits to the rate of adaptive responses, through genetic, behavioural or ecological mechanisms remains a critical gap in understanding. Recent theoretical and empirical studies are starting to reveal those factors that will limit the rate and effectiveness of adaptation, but an overall predictive framework remains elusive and the complexities are unlikely to be resolved soon.

How might this affect the IPCC statement?

There is very strong evidence that changes in population abundance and local extinctions are common responses to a changing climate and that these increase with greater rates and intensities of climate change (see Figure). New findings do not change the IPCC message. Increasingly detailed understanding highlights yet more uncertainty about the rate of extinction and about the most strongly affected species and ecological communities.

Robust risk assessment and modelling methods, to guide conservation decisions being taken now, remain a research priority. Traditional conservation actions, such as species conservation planning and protected areas, have been shown to continue to be effective, even in a rapidly changing environment.

QUESTION THIRTEEN – How will aspects of human health be affected by climate change?

Summary

Human health will be affected by climate change in multiple ways, with imacts including those from extreme heat, food availability and changes in the geographical occurrence of infectious diseases.

In AR5 IPCC said:

Throughout the 21st century, climate change is expected to lead to increases in ill-health in many regions and especially in developing countries with low income, as compared to a baseline without climate change.

What is this about?

The human health effects of climate change are an important concern in seeking to keep warming below 2°C (or 1.5°C). These occur through several mechanisms with a variety of impacts. This section considers some new research on a limited subset of these mechanisms: the impacts of changes in exposure to heat stress, increased infectious disease risk, and effects on nutrition.

These are clearer now than before AR5. Other impacts, including potentially far-reaching effects mediated through social and economic disruption such as increasing poverty, conflict, and migration are not considered here.

What was the basis for the statement in AR5?

AR5 considered that climate change will act initially by exacerbating existing health problems. It is likely that rising temperatures have already increased the risk of heat-related death and illness. Particularly under high emissions scenarios, impacts on health were expected to increase substantially and to be greatest where other stressors, promoted by low economic and social development, inhibit adaptation and resilience.

What do we know now?

Since the IPCC AR5 report there have been a number of new estimates of the extent to which populations will be exposed to extreme levels of heat. For example recent work shows that, even with global warming of only 1.5°C and midrange population growth, over 350 million more people could be exposed to hazardous levels of heat by 2050 in cities such as Lagos and Shanghai.

Another new study identified a threshold in air temperature and relative humidity beyond which increased deaths occur. Around 30% of the world’s population is currently exposed, for at least 20 days a year, to conditions exceeding this threshold. By 2100, this percentage is projected to increase to around 48% under an intermediate emission pathway (RCP 4.5) and around 74% under high emissions pathway (RCP8.5) (see Figure).

Social adaptation could reduce exposure to these conditions, but would not affect their occurrence.

High income regions will also experience serious consequences and a study of ten large metropolitan areas in the USA showed that under a high emissions scenario towards the end of the century eight of them would experience increases in heat related deaths exceeding projected reductions in cold related deaths, in some cases by a large amount. Furthermore substantially fewer deaths are projected under a lower emissions scenario.

Results of large multi-country analyses indicates that increased heat-related deaths will greatly exceed reductions in cold-related mortality in some regions particularly under high emission scenarios, in particular warmer and poorer areas that are projected to include a substantial proportion of the global population. Most studies on the effects of temperature have focused on adults but a recent study of seven cities in Korea shows substantial increases in infant mortality, both total and from sudden infant death syndrome (SIDS), with high temperatures in the period before death.

Dengue accounts for about 390 million infections annually. The two main mosquito vector species are affected by multiple drivers including climate change. Several modelling studies since 2013 have confirmed that climate change would cause dengue to expand into areas at the edge of current distribution ranges. One study suggests that the population exposure to the main vector (as well as other diseases spread by mosquitoes) would increase by 8 – 12% due to climate change alone, amplifying the larger increase in exposure caused by population growth.

The complex influence of climate change on health via nutrition is illustrated by a modelling study which projected that by 2050, climate change will lead to per- person reductions of about 3% in global food availability compared to a reference scenario, together with an important reduction in fruit and vegetable consumption. These declines are estimated to lead to a net increase of about 500,000 deaths annually.

How might this affect the IPCC statement?

The new evidence discussed above provides a basis for replacing qualitative statements with more quantitative ones, and for targeting specific adaptation and mitigation strategies that can reduce the excess fatalities incurred.

Appendix
This section explains some of the methodology and terminology used in the remainder of the report.

Methodology

This report touches on a limited list of topics, considered by the working group to be areas of particular interest or progress in recent years. They are by no means a comprehensive list of issues that are discussed in the scientific literature or in popular articles. For example, quantifying the role of aerosols (small particles in
the atmosphere) in climate is important, but is not covered here.

For each topic, the most relevant conclusion from the AR5 was chosen, and a lead author and critical reviewer were appointed from within the working group authorship.

Authors surveyed recent literature to examine work (including review articles) that addressed the chosen IPCC quotation and other relevant conclusions. They used this, contributions from other researchers and their expert judgement to produce the final sections, which were discussed and agreed by the whole group.

Peer review was then undertaken by a small review group (consisting of people not involved in the drafting), and final revisions were made on the basis of their comments.

This process is far below the level of scrutiny that is carried out over several years by writing teams in producing the IPCC statements. However we believe that we have captured the main advances, confirmations, and new issues that have arisen, allowing us to assess whether the IPCC statements remain valid.

IPCC and terminology

The IPCC Fifth Assessment Report (AR5) was produced in stages. The Working Group (WG) 1 report was published in 2013, WG2 and 3 in 2014, and the synthesis report in 2015. However for inclusion in the report, findings had to have been submitted into the literature at different dates in 2013 for all 3 WG reports. For this reason, we assess here findings that have appeared in the literature since the cutoff dates in 2013, and this is what we mean when we refer to advances “since AR5” or “since the last IPCC report”.

The next full IPCC report is due to be finalised in 2022, with WG reports ready in 2021. There will also be three special reports:

  1. The Special Report on Global Warming of 1.5°C (SR15) will be finalised in September 2018;
  2. Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC),
  3. Special Report on Climate Change and Land (SRCCL) will be finalised in September 2019.

These will provide a more authoritative conclusion on some of the issues we consider.

In making projections about future change AR5 used 4 different ‘representative concentration pathways’ (RCPs). These are time series of future greenhouse gas and aerosol concentrations intended to represent the results of different scenarios, in particular for socioeconomics and energy use. These RCPs were used as the input to climate models in many cases.

The pathway with the lowest concentrations of greenhouse gases, RCP2.6 represents scenarios with extreme mitigation measures, much beyond those currently agreed between nations. The highest concentration scenario, RCP8.5, represents a highly industrialised, low mitigation scenario.

In the report we sometimes refer to a high or low emissions scenario. Most often in such cases we are referring to model studies using RCP8.5 or RCP2.6 respectively, although occasionally this refers to studies using a previous generation of scenarios. The supplementary information will, where appropriate, use the technical terminology that the main text avoids.

Throughout IPCC publications, levels of confidence and uncertainty in statements are described using calibrated language. Confidence is described as from ‘very low’ to ‘very high’ based upon the level of evidence and agreement between sources, and likelihood is described from ‘exceptionally unlikely’ (≤ 1% probability) to ‘virtually certain’ (≥ 99% probability).

Such terms have been retained in the IPCC quotations, but elsewhere in this report they are not used with these calibrated meanings.

Working Group members

The members of the Working Group involved in producing this report are listed below. The Working Group members acted in an individual and not organisational capacity and declared any conflicts of interest. They contributed on the basis of their own expertise and good judgement. The Royal Society gratefully acknowledges their contribution.

Working Group

Professor Eric Wol FRS (Chair) University of Cambridge
Professor Nigel Arnell University of Reading
Professor Pierre Friedlingstein University of Exeter
Professor Jonathan Gregory FRS University of Reading / Met Office Hadley Centre
Professor Joanna Haigh CBE FRS Imperial College London
Sir Andy Haines FMedSci London School of Hygiene and Tropical Medicine
Professor Ed Hawkins University of Reading
Professor Gabriele Hegerl FRS University of Edinburgh
Sir Brian Hoskins CBE FRS Imperial College London
Dame Georgina Mace DBE FRS University College London
Professor Iain Colin Prentice Imperial College London
Professor Keith Shine FRS University of Reading
Professor Peter Smith FRS University of Aberdeen
Professor Rowan Sutton University of Reading
Dr Carol Turley OBE Plymouth Marine Laboratory

Royal Society staff

Many staff at the Royal Society contributed to the production of this report. The project team are listed below.

Royal Society staff

Helene Margue Policy Adviser
Elizabeth Surkovic Head of Policy, Resilience and Emerging Technologies
Dr Richard Walker Senior Policy Adviser

Review panel
This report has been reviewed by a number of independent experts. The Review Panel members were not asked to endorse the conclusions of the report, but to act as independent referees of its technical content and presentation.

Panel members acted in a personal and not an organisational capacity and were asked to declare any potential conflicts of interest. The Royal Society gratefully acknowledges the contribution of the reviewers.

The Review Panel

Professor Stephen Belcher Met Office Hadley Centre
Professor Alex Halliday FRS Vice-President, Royal Society
Professor Gideon Henderson FRS University of Oxford
The Lord Krebs Kt FMedSci FRS University of Oxford
Professor Yadvinder Malhi FRS University of Oxford
Professor John Mitchell FRS Met Office Hadley Centre
The Lord Oxburgh KBE HonFREng FRS House of Lords
Professor Tim Palmer CBE FRS University of Oxford
Professor John Shepherd CBE FRS University of Southampton
Professor Theodore Shepherd FRS University of Reading
Dr Emily Shuckburgh British Antarctic Survey
Dame Julia Slingo DBE FRS Former Chief Scientic Adviser, Met Office Hadley Centre

Acknowledgments
This project would also not have been possible without contributions from a range of individuals. In particular we wish to thank:

Acknowledgements

Professor Andrew Challinor, University of Leeds
Dr Ed Dlugokencky, US National Oceanic and Atmospheric Administration
Natalya Gallo, Scripps Institution of Oceanography
Dr Mario Herrero, The Commonwealth Scientific and Industrial Research Organisation
Chris Jones, Met Office Hadley Centre
Professor John Roy Porter, Supagro Montpellier
Professor Corinne Le Quere FRS, University of East Anglia
Dr Richard Pearson, University College London
Dr Doug Smith, Met Office Hadley Centre
Dr Peter Stott, Met Office Hadley Centre
Professor Chris Thomas FRS, University of York
Professor Mark Urban, University of Connecticut
Dr Phillip Williamson, University of East Anglia
Dr Richard Wood, Met Office Hadley Centre
Dr Tim Woollings, University of Oxford

The Royal Society

The Royal Society is a self-governing Fellowship of many of the world’s most distinguished scientists drawn from all areas of science, engineering and medicine. The Society’s fundamental purpose, as it has been since its foundation in 1660, is to recognize, promote and support excellence in science and to encourage the development and use of science for the benefit of humanity.

The Society’s strategic priorities emphasize its commitment to the highest quality science, to curiosity-driven research, and to the development and use of science for the benefit of society. These priorities are:

* Promoting excellence in science
* Supporting international collaboration
* Demonstrating the importance of science to everyone