The House of Commons Energy and Climate Change Committee report on the Working Group 1 contribution to the IPCC Fifth Assessment Report, which is published today, has found the IPCC process to be robust. The committee launched an inquiry into the IPCC WG1 report in October 2013, following criticism by some commentators of the IPCC review process and its conclusions.
The Grantham Institute submitted written evidence to the committee (you can read our evidence here) and our Chair Professor Sir Brian Hoskins was called before the committee to give oral evidence.
The committee found that “the IPCC has responded extremely well to constructive criticism in the last few years and has tightened its review processes to make its Fifth Assessment Report (AR5) the most exhaustive and heavily scrutinised Assessment Report to-date. The MPs call on the IPCC to continue to improve its transparency, however. The IPCC would benefit, they say, from recruiting a small team of non-climate scientists to observe the review process and the plenary meetings where the Summary for Policymakers is agreed.”
Commenting on the report Professor Joanna Haigh, Co-Director Grantham Institute said:
“Having assessed a significant quantity of submitted evidence, both written and oral, this report is overwhelmingly supportive of both the procedures and the conclusions of the IPCC. It concludes that the WG1 report is the best available summary of the state of the science of climate change, that improvements to IPCC procedures since the Fourth Assessment have ensured “the highest Quality of scholarship” and that there is no scientific basis for downgrading UK’s ambition to reduce greenhouse gas emissions.
In terms of procedures it recommends two areas of further improvement – the appointment by governments of some non-climate scientists as members of the Executive Committee, and to observe the review process, and a greater level of transparency in plenary meetings discussing the Summary for Policymakers – but these recommendations in no way reflect concern about the content of the Assessment. A whole chapter of the report is devoted to examining criticisms that have been levelled, from both inside and outside the scientific community, on the scientific conclusions but none is found to have significant bearing.
Such a robust report from an all party parliamentary committee surely means that we can now reduce efforts spent on dealing with the constituencies working to discredit the IPCC, concentrate on understanding the science behind climate and climate change and do our best to make sure that the government plays a leading role in achieving a global deal on climate change.”
Professor Sir Brian Hoskins, Chair of the Grantham Institute said:
“The committee recognises that the recent WG1 report of IPCC gives a very good summary of the science relevant to climate change, whilst there are some remaining issues on transparency.
The question now is how do we respond to the risk posed by climate change, and I am pleased to see that the Report is clear: it supports the basis for the advice given by the Climate Change Committee and the path the UK is taking towards its 2050 carbon reduction target, in particular the 4th Carbon budget recently confirmed by Government, it advises that the UK Government at the top level should play a major role in international discussions leading up to Paris 2015.”
Following on from Simon Buckle’s post this morning another piece of good news on emissions reductions, the UK government has announced that they will not amend the fourth carbon budget, after reviewing their commitments in light of progress within the EU.
Therefore the carbon budget for 2023-27 remains at 1,950 MtCO2e, keeping the UK on track to reduce greenhouse gas emissions by 2050 by 80% relative to 1990 levels.
There was some good news last week from the annual Petersberg Climate Dialogues held on 14-15 July in Berlin. The Petersberg meetings were instituted after the perceived failure of the Copenhagen summit in 2009 in order to support the UNFCCC talks. They are co-chaired by Germany and the country hosting the next Conference of the Parties meeting, in this case Peru.
Chancellor Merkel took the opportunity in her address to signal renewed ambition for climate action, perhaps disappointing some of those who had been hoping (or even working) for a reversal of Germany’s commitment to decarbonisation. As reported by EurActiv, Merkel said that “A turnaround is needed – worldwide“. Making it clear that she intends to re-energise climate change mitigation, she noted that Germany aims to cut its own CO2 emissions by 40% by 2020 (relative to 1990 levels) and that “Europe will be making an “ambitious contribution” to the forthcoming UNFCCC negotiations that should result in a new climate agreement at the Paris conference in 2015. Of course, the current European Commission proposal to be discussed in October is somewhat less ambitious, reflecting largely East European concerns, and proposes a 40% reduction of EU-wide emissions only by 2030.
The final statement by the German and Peruvian co-Chairs repeated the point I have been making over the past few months to a number of national climate negotiators and the UNFCCC Secretariat and which was the subject of my 3 July blog. This is that “there was a need for [national] contributions in aggregate to meet the overall ambition of maintaining temperature increase below 2°C. In order to ensure this happens, some Ministers acknowledged that a process for collectively considering intended nationally determined contributions was necessary.” Progress, if not yet complete agreement.
The sense of greater momentum was reinforced by the announcement by the Vice President of the Chinese National Development and Reform Commission, Xie Zhenhua, that as part of its contribution to the Paris agreement, it may set a date for the peaking of its own emissions.
Just a couple of months before the UN Secretary General’s climate summit on 23 September, the political climate looks a lot brighter than it has for a long while. Achieving what I see as the first and most significant step on the global mitigation pathway – a peak in global fossil-related carbon dioxide emissions, ideally before 2030 – is the sort of inspirational but realistic target that leaders should now embrace for the Paris agreement if we are to make the most of this opening window of opportunity to limit future climate risks.
In an article for the Telegraph, Christopher Booker gave his views on Professor Sir Brian Hoskins’ appearance on the Today programme earlier this year. In the article, Booker made several claims about climate science relating to rainfall, atmospheric humidity, polar sea ice extent, global temperatures and sea level rise. In this blog I will assess his claims against the findings of the latest report of Working Group 1 of the Intergovernmental Panel on Climate Change (IPCC), a hugely comprehensive assessment of the scientific literature.
Rainfall and floods
Booker’s comment: “Not even the latest technical report from the UN’s Intergovernmental Panel on Climate Change (IPCC) could find any evidence that rainfall and floods were increasing.”
Scientific Evidence:
The IPCC report found a significant climate influence on global scale changes in precipitation patterns (with medium confidence), including increases in precipitation in northern hemisphere mid to high latitudes. Further evidence of this comes from the observed changes in sea level salinity, an indication of the global distribution of evaporation and precipitation. The data is currently too inconclusive to report other regional changes in rainfall with confidence. Overall, however, there had been little change in land-based precipitation since 1900, contrasting with their 2007 assessment, which reported that global precipitation averaged over land areas had increased.
The IPCC concluded that there continues to be a lack of evidence and thus low confidence regarding the sign of trend in the magnitude and/or frequency of floods on a global scale.
The IPCC’s projected short-term changes (2016-35) in rainfall were:
Increased mean precipitation in the high and some of the mid latitudes (very likely)
Reductions in the sub-tropics (more likely than not).
There is also likely to be an increase in the frequency and intensity of heavy precipitation events over land. Regional changes will be strongly affected by natural variability and will also depend on future aerosol level (emissions and volcanic) and land use change.
Global rainfall totals are expected to go up in the longer term (i.e. beyond 2035) by around 1-3% per degree Celsius of global mean surface temperature increase, except in the very lowest emissions scenario.
Booker is partially right on past changes: the IPCC found no significant trend in global average rainfall over land. But this is not to say there has been no effect. Indeed, the expected increase in extreme heavy rain is already happening: the IPCC concluded with medium confidence that since 1951 there has been an increase in the number of heavy precipitation events in more regions than have had a decrease.
Booker’s comment: “From the official National Oceanic and Atmospheric Administration (NOAA) satellite data on humidity (shown on the “atmosphere page” of the science blog Watts Up With That), we see it has actually been falling.”
Scientific Evidence:
The key measure of whether atmospheric humidity is rising or falling is specific humidity, i.e. the mass of water vapour in a unit mass of moist air. The “atmosphere page” of “Watts Up With That” when accessed on 17 July wrongly shows data on relative humidity under the heading “Specific humidity”. Relative humidity is a measure that depends on temperature and does not therefore measure the absolute water vapour content of the atmosphere. In other words, Booker’s evidence is not evidence.
The latest IPCC report concludes that it is very likely that global near surface and tropospheric air specific humidity have increased since the 1970s. However, during recent years the near-surface moistening trend over land has abated (medium confidence). The magnitude of the observed global change in water vapour of about 3.5% in the past 40 years is consistent with the observed temperature change of about 0.5°C during the same period. The water vapour change can be attributed to human influence with medium confidence.
Polar ice melt
Booker’s comment: “As for polar ice, put the Arctic and the Antarctic together and there has lately been more sea ice than at any time since records began (see the Cryosphere Today website).”
Scientific Evidence:
The IPCC found that since 1979, annual Arctic sea ice extent has declined by 0.45-0.51 million km2 per decade and annual Antarctic sea ice extent has increased by 0.13-0.20 million km2 per decade. Taking the two IPCC estimates together, it can be inferred that total global sea ice extent has declined since 1979.
Sea ice thickness is harder to measure. The IPCC combined submarine-based measurements with satellite altimetry, concluding that Arctic sea ice has thinned by 1.3 – 2.3 m between 1980 and 2008. There is insufficient data to estimate any change in Antarctic sea ice thickness.
The reason why the Arctic sea ice has declined and the Antarctic sea ice hasn’t is because they have very different characteristics. Arctic sea ice is constrained by the North American and Eurasian landmasses to the south. In the central Arctic Ocean, the ice can survive several years, which allows it to thicken to several meters. Due to climate warming, the Arctic summer minimum has declined by around 11.5% per decade since 1979, and the extent of the ice that has survived more than two summers has declined by around 13.5% per decade over the same period. This has serious consequences for the surface albedo (reflectance) of the Arctic, as a reduction in the highly reflecting sea ice with less reflective open water results in enhanced absorption of solar radiation.
In contrast to the Arctic, Antarctic sea ice forms in the open ocean with no northern land to constrain its formation. The vast majority of Antarctic sea ice melts each summer.
Booker mentioned sea ice specifically, but he did not mention the other important components of the global cryosphere. Making use of better observations than were available at the time of their previous report in 2007, the IPCC carried out an assessment of all the ice on the planet and concluded that there had been a continued decline in the total amount of ice on the planet. The Greenland and Antarctic ice sheets are both losing mass (with very high confidence and high confidence respectively). Glaciers are known to be declining globally (with very high confidence). Overall snow cover, freshwater ice and frozen ground (permafrost) are also declining, although the available data is mostly for the Northern hemisphere.
Temperature
Booker says: “As for Sir Brian’s claim that by 2100 temperatures will have risen by a further ‘3-5oC’, not even the IPCC dares predict anything so scary.”
Scientific evidence:
Future temperature rise of course depends on greenhouse gas emissions. In the lowest of the IPCC emissions scenarios, which assumes that global carbon dioxide emissions will decline after 2020, reach zero around 2080, and then continue dropping to just below zero by 2090, temperatures are projected to increase by another 0.3oC – 1.7oC by 2100. Total warming under this scenario is projected to be 0.9oC – 2.3oC relative to 1850-1900, i.e. including warming over the 20th century. Under the highest emissions scenario, the closest to business as usual, another 2.6oC – 4.8oC of warming is projected by 2100. In this case, the total projected temperature rise by 2100 is 3.2oC – 5.4oC when past temperature rise is included.
It is worth emphasising that if emissions are not constrained then we are likely to see a temperature rise of the same order as the projections under the IPCC’s highest emissions scenario. All three of the other scenarios assume that carbon dioxide emissions will peak and then decline substantially at some point in the coming decades. If emissions continue to rise then we should expect a total temperature increase in the region of 3.2oC – 5.4oC by the end of the century. This can of course be avoided if action is taken to reduce fossil fuel dependency.
Booker says: “[Professor Hoskins] was never more wobbly than when trying to explain away why there has now been no rise in average global temperatures for 17 years, making nonsense of all those earlier IPCC computer projections that temperatures should by now be rising at 0.3C every decade.”
Scientific evidence:
Figure 1: Past global surface temperature rise according to the MLOST, HadCRUT4 and GISS datasets (IPCC, 2013). There is a long term increase in temperature, but also natural variability.
Climate change is a long term trend, and a few decades worth of data are needed to separate the warming trend from natural variability. Global mean surface temperature increased by about 0.85oC over the period 1880-2012. Each of the last three decades has been warmer than all previous decades in the instrumental record and the decade of the 2000s has been the warmest.
The observed temperature record over the 20th Century shows periods of slower and faster warming in response to a number of factors, most notably natural variability in the climate system, the changes in atmospheric composition due to large-scale human emissions of greenhouse gases and aerosols from burning fossil fuels and land-use change, volcanic activity and small changes in the level of solar activity.
In future, there will continue to be natural variation in temperature as well as a long term warming trend due to our greenhouse gas emissions. Significant natural climate variability means that a prolonged continuation of the current slowdown in the rate of increase would not on its own be strong evidence against climate change, provided that: 1) the global mean sea level continued to rise due to thermal expansion of the oceans, the melting of glaciers and loss of ice from ice sheets, and 2) the measured net energy flow into the climate system (predominantly the ocean) remained significantly positive.
The climate models used by the IPCC are not designed to predict the exact temperature of the Earth surface in a particular year or decade. This would require scientists to predict the future state of climatic phenomena such as the El Niño Southern Oscillation or the Pacific Decadal Oscillation for a specific period several years in advance, something that is not currently possible. Volcanic eruptions also have an impact on global temperatures, and they are not known about far enough in advance to be incorporated into the IPCC’s model projections.
Figure 2: The future projected increase in global surface temperature (IPCC, 2013). All the results are based on several model runs (numbers of model runs shown in the appropriate colours). The red line shows the highest emissions scenario, the closest to business as usual. The dark blue line shows the lowest emissions scenario, which assumes continued reductions in emissions after 2020, and the other two lines (orange and light blue) are intermediate scenarios.
Sea level rise
Booker says: “NOAA’s data show that the modest 200-year-long rise in sea levels has slowed to such an extent that, if its recent trend continues, by the end of the century the sea will have risen by less than seven inches.”
Scientific evidence:
Figure 3: Past sea level rise according to six datasets (IPCC,2013). These are based on tide gauge measurements – satellite data is included after 1993.
The IPCC assessed the relevant data carefully and concluded that sea level rose by around 19 cm (about 7 ½ inches) between 1901 and 2010. This is based on tide gauge data, with satellite data included after 1993. The rate of sea level rise was around 3.2 mm (about 1/8th inch) per year between 1993 and 2010. This is faster than the overall rate since 1901, indicating that sea level rise is accelerating as would be expected from thermal expansion of seawater and increased melting of ice on land.
Future sea level projections under the highest IPCC emissions scenario tell us what is likely to happen if emissions continue to rise unabated. In this case, sea level is projected to increase by a further 63 cm (about 24 ¾ inches) in the last two decades of this century compared with the 1986-2005 average. Even in the lowest emissions scenario, which requires substantial emissions reductions, another 40 cm (about 15 ¾ inches) of sea level rise can be expected by 2100.
IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp.
Helena Wright, an Imperial PhD student, looks at worst possible scenarios from the IPCC Working Group II report.
The United Nations’ Intergovernmental Panel on Climate Change (IPCC) recently released its latest report, featuring the most up-to-date science on global climate change.
As a researcher, I had an opportunity to contribute to a table in one of the chapters and have read through each of the 30 chapters of the Working Group II report (on Impacts, Adaptation, and Vulnerability). Here is my personal take on seven of the most frightening findings from the WG2 report:
CO2 levels of 1000ppm could impact on mental performance
The health chapter explains how climate change will affect global health, including direct impacts of heat stress, drought and extreme events, as well as indirect impacts on nutrition and mental health.
One extremely frightening direct effect could actually be from CO2 itself. A recent study found indoor CO2 levels of 1000ppm (parts per million) can impair human decision-making performance and cognition. Current atmospheric levels are 400ppm and rising fast. Some scenarios have us reaching these levels by 2100. If these effects are confirmed, how will we be able to adapt?
Climate stress affects children
One particularly frightening aspect of climate change is its impact on children. This is a long term problem with implications for future generations.
Coral reefs would degrade under 2 degrees of warming
The coastal chapter explains carbonate reef structures would degrade under a scenario of 2°C by 2050-2100. Increasing levels of atmospheric CO2 also cause the ocean to acidify, causing coral reefs to lose their structural integrity. The North Atlantic and North Pacific are already becoming more acidic.
Coral reefs are important for biodiversity and account for 20-25% of fish caught in developing countries, as well as housing many other marine creatures. Skeletal “dissolution” is expected to be widespread by 2100. The most frightening thing of all is that these are the impacts under business-as-usual scenarios. Average global temperature has already risen by 0.8°C since 1880. Global leaders have only agreed to limit warming to 2°C of warming, a target they are currently missing.
Climate extremes threaten our food security
Over 70% of agriculture is rain-fed, so agriculture and food security are highly sensitive to changes in rainfall. Higher temperatures have an impact on crop yields. Climate change will affect rivers and oceans as well. Some scenarios forecast widespread fish extinctions in rivers. In one study where data was available, as much as 75% of local fish biodiversity would be ‘headed toward extinction’ by 2070 due to climate change, particularly in tropical areas.
Food price rises triggered by climate shocks disproportionately affect the poor who tend to spend a higher proportion of their income on food.
Global trade will be affected
Climate change will impact on international trade in both physical and value terms. For example, coffee is a major traded beverage which is sensitive to climate variability. Coffee crops will be forced to move to higher altitudes where they are available. Millions of rural people rely on coffee, tea and cocoa production.
The economic costs are expected to be huge. For example, in Ethiopia, agricultural decline is projected to cause a 10% decline in GDP against benchmark levels. While trade can help countries to adapt, for example by importing food, deficits may have to be met by food aid.
Climate change will impact on migration, and could lead to conflict and even wars
High food prices can impact on socio-political stability. For example, 14 countries in Africa experienced food riots in 2008 during the 2008-9 price spike.
People can also be displaced by extreme weather events. But migrants do not necessarily reach safety; with new migrants more at risk at destinations in cities. Sea level rise is projected to lead to permanent displacement as coastal areas become uninhabitable. Under 2 metres of sea level rise, 187 million people are expected to be displaced.
Chapter 12 also examines research on links between climate change and armed conflict. Many of the factors that increase the risk of civil war are sensitive to climate change. US Military experts recently called climate change “a catalyst for conflict”.
There are limits to adaptation
Finally, there are limits to adaptation. This means we cannot adapt to many of these impacts. For example, 31 Native Alaskan villages are facing “imminent threats” due to coastal erosion and several decided to relocate – but their ability to relocate also depends on financial support. Examples of ‘hard’ limits to adaptation include water supply in fossil aquifers, limits to retreat on islands, and loss of genetic diversity. In such cases climate change will lead to irreversible losses.
There are various ‘tipping points’ in the earth system which, if crossed, could trigger rapid and catastrophic climate change. Only mitigation can avoid such risks. Unfortunately little is known about where exactly these ‘thresholds’ lie, making the risks even more difficult to manage.
The limits to adaptation explain why global emission reduction is so vital for humanity. 3-4 degrees of warming would be much more difficult to adapt to than 2 degrees to and could result in the collapse of systems. Yet current climate pledges leave us heading to a world 3.7 degrees warmer. The IPCC shows global emissions are still rising rapidly and show no signs of stabilising. We are entering a radically different world.
However, there are reasons for hope. The UNFCCC negotiations took place again last month in Bonn, with the aim of reaching a global climate deal. There are signs of leadership from the US and China, the worlds’ two biggest emitters, offering renewed hope that collectively we can tackle this problem.
I spent a few days at the recent Bonn climate change conference (4-15 June) during the High Level Ministerial events on 5-6 June. Not that these were the most interesting things happening there. Unsurprisingly, by and large, Ministers did not stray from well rehearsed positions, reflecting the continued skirmishing over the interpretation of the UN Framework Convention on Climate Change (UNFCCC) term “common but differentiated responsibilities” in a world that is radically different from the one in which the Convention was conceived.
More interesting were the briefing session on the UN Secretary General’s forthcoming climate summit in New York on 23 September and a series of special events where negotiators got the chance to hear from and question IPCC authors about the implications of the IPCC AR5 reports for the UN negotiations and the review underway of the long-term target (2°C or 1.5°C?), a key issue for vulnerable countries (e.g. small island states) given the very different potential implications of sea-level rise. It’s worth looking at some of the webcasts.
A particularly revealing moment came during a special event to engage with Observers to the UNFCCC process organised by the co-chairs of the so-called “Ad Hoc Working Group on the Durban Platform for Enhanced Action” (ADP). The ADP is the subsidiary body charged with developing the Paris 2015 agreement as well as trying to identify ways to enhance mitigation action before 2020.
As part of the ADP process, early in 2015 countries should notify the UNFCCC Secretariat of their “intended nationally determined contributions” (INDCs) to emissions reductions in the period after 2020. I therefore asked the ADP co-chairs how the UN process would ensure that these bottom-up contributions – and the aggregate global emissions that they implied – would be consistent with the long-term climate targets that countries had committed to. This was indeed a critical issue they said, but they had as yet no idea how this might be achieved.
This seems to me to be a pretty fundamental problem. An aspiration to achieve “a carbon neutral world in the second half of the century” (the current UNFCCC thinking on such an overarching aim) is in my view just not good enough to constrain climate risks and achieve a cost-effective transition to a low-carbon world. In particular, it says nothing about the emissions path over the next 30 years or so.
We know that effective international action on climate is difficult to achieve given the concerns over competitiveness and free-riding. So instead of the top down approach to earlier climate agreements (i.e. Kyoto with it modest targets and timetables) or the bottom-up approach that has now emerged by default from the political trauma of the 2009 Copenhagen summit, we now need a hybrid approach. What I have in mind is that the aggregate bottom-up emissions pledges under the UN process need to be supplemented and given coherence by a political commitment among the major emitting economies – notably the US, China and the EU – to achieve a clear, measurable and negotiable near-term mitigation objective, which would be reflected within the Paris agreement. My own suggestion for what this objective should be is that it should commit to achieving a global peaking in fossil-related carbon dioxide emissions by 2030 or earlier if possible, with a subsequent decline.
Recent developments in the US and China suggest that such a goal is not impossible, particularly if the EU can get its act together and agree its 2030 targets at the October Council. Moreover my own calculations suggest a global peak in fossil carbon dioxide emissions could be achieved while allowing developing country emissions (e.g. in India) to continue to grow for some time to come, as they must in any politically viable deal.
Of course achieving a global peak in carbon dioxide emissions is just a first step on the road to a longer term objective and if it is achieved too late or the peaking level is too high, we may not be able to achieve some of the more stringent climate targets. But if we just focus on the long term target, we will end up in a zero-sum negotiation over the level and shares of a corresponding fixed carbon budget consistent with this target. The urgent need at this point in time is to reverse the continuing growth in global CO2 emissions, a necessary first step in achieving any long-term goal. The pace of emissions reductions after the peak and the eventual level of emissions in the second half of the century can be agreed at future summits.
No doubt there are several other ideas for making Paris a success being discussed by governments in private as I write. One might be to build in flexibility to the Paris agreement itself and have short commitment periods, perhaps to 2025 initially but agreed on a rolling five years basis thereafter, mirroring the UK approach to setting carbon budgets. And there needs to be far more public discussion about these alternatives. But these technical suggestions are worthless without political leadership. The next 18 months presents an unprecedented opportunity to shift the world decisively onto a cost-effective, low climate-risk development path, with myriad benefits for our wellbeing and economic development. The Secretary General’s September summit will be an early indication of whether our political leaders are ready to make this step or not.
The House of Commons Energy and Climate Change Committee report on the Working Group 1 contribution to the IPCC Fifth Assessment Report, which is published today, has found the IPCC process to be robust. The committee launched an inquiry into the IPCC WG1 report in October 2013, following criticism by some commentators of the IPCC review process and its conclusions.
Following on from Simon Buckle’s post this morning another piece of good news on emissions reductions, the 
