Portal de Periódicos da CAPES

History of climate science

2022; Wiley; Volume: 77; Issue: 8 Linguagem: Inglês

10.1002/wea.4245

1477-8696

P. D. Jones,

Geology and Paleoclimatology Research

The meeting began with a recorded introduction by David Warrilow, who was unable to attend in person. David gave a brief history of climate science and how this has impacted UK Government Policy over the period since the late 1980s. David expanded on this in a more detailed summary at the end of the meeting. The meeting was recorded by the Royal Meteorological Society and is available online 1 1 Recording available on the RMetS YouTube channel: https://www.youtube.com/watch?v=iHQ7aD9aAT8. . Sir Brian Hoskins (UCL and Reading) began the live proceedings by recalling his first talk on climate change in the late 1970s to the Clean Air Society at Scarborough. He briefly discussed the subjects that would be covered during the day, highlighting some of the history of Dynamical Meteorology that would not be covered. This pointed to the complementary initiatives from the Met Office and UK Universities in the development of numerical models, all building on eminent earlier scientists such as Halley, Hadley, Rossby and Lorenz. Brian then gave way to Chris Folland who chaired the session during the day. Chris had led the team who put the whole session together back in 2019, which was subsequently delayed by COVID-19. An advantage of the long delay was that two of the three working groups of the IPCC AR6 report had reported in August 2021 and February 2022. Liz Thomas (BAS) was the first main speaker, discussing longer-term perspectives from ice cores, particularly those from the Antarctic extending back 800k years. The synchroneity of isotopic-inferred temperatures with carbon dioxide and methane concentrations was clear, with previous interglacials often being warmer than the Holocene despite carbon dioxide concentrations of about 280 ppm, in contrast to today's levels of almost 420 ppm. The last 130k years were contrasted with the Arctic (the current oldest ice from Greenland) which showed much more dramatic and rapid variations than the Antarctic. Homo sapiens developed mostly during the last 200k years, so had to cope with rapid changes in climate (such as the cooling during the 8.2k years ago event). Liz concluded by showing that Antarctic reconstructions depend on many factors, particularly elevation changes across West Antarctica during the Eemian interglacial, and that snowfall increases in parts of Antarctica have mitigated sea level rise since 1900, with this trend likely to continue out to 2100. Joanna Haigh (IC) discussed the history of the science of the greenhouse effect, showing who did what, when and why, and also how many of the terms they used differed somewhat from how we understand them today. Amongst those covered were Joseph Fourier, Eunice Foote and John Tyndall, but it wasn't until Svante Arrhenius in the late nineteenth century that the potential of increasing carbon dioxide from fossil fuel burning was extrapolated to the future. Arrhenius calculated a doubling of carbon dioxide might lead to a warming of 5–6 degC. The often neglected Guy Stewart Callendar (a steam engineer, for whom climate science was a hobby) was the first to bring together measurements of carbon dioxide concentration with how much the world had warmed from the late-nineteenth century in two key papers in QJRMS (in 1938 and 1961). Callendar was mentioned by two other speakers during the day. Joanna also noted those who were sceptical of the importance of carbon dioxide (Knut Angstrom who erroneously stated that the carbon dioxide absorption bands were swamped by water vapour, and later ideas in the 1950s that carbon dioxide was being taken out of the atmosphere by the oceans much more than in reality). Joanna was the first of several speakers to note that the latest AR6 report of WG1 of IPCC had reduced the range of climate sensitivity to between 2.5 and 4.0 degC. Sarah Dry (University of Cambridge) then gave her talk from a history of science perspective, addressing how climatology had become a science of change. She began with the pioneering work in the early nineteenth century by Alexander von Humboldt to develop isotherm maps of the world. Late nineteenth and early twentieth century work of Julius von Hann and Wladimir Köppen further developed climate averages and classification schemes. This geographical basis of climatology was then transformed by Wilhelm Bjerknes to solve the Navier–Stokes equations to model the weather and climate leading to predictions. With early computers in the late-1940s and their continued and rapid improvement, the emphasis in climate science was on solving the equations while the geographical aspects of climatology (collecting the evidence) seemed less important. Despite this, many new palaeoclimatic sources were being developed from the 1960s to the present. In addition, the collection of instrumental data both on land and sea from the eighteenth century, has gradually been digitized since the 1960s, and is now mostly available for all climate scientists to use. Tim Osborn (CRU, UEA) began the afternoon on Global Temperature data and who had produced early compilations: Köppen in 1881 and Callendar in 1938 and 1961. Both were aware of the limited early networks, as they assessed the uncertainties involved, and also the issues of data quality and potential inhomogeneities. At that time, the best they could do was to remove any stations that disagreed with neighbouring sites. The gradual standardization of measurements (the use of variants of Stevenson screens) and different national standards of estimating daily and hence monthly averages were noted. The number of stations needed to produce hemispheric or global averages depends on timescale, with fewer on decadal and annual timescales. Comparisons of Callendar's results against later datasets with 10–20 times more stations show that a limited number of sites produce excellent land-based time series. Many more stations are needed to get all the spatial details. Land regions comprise only 30% of the Earth's surface, and near-global coverage has been achieved using anomalies of sea surface temperatures. A recent NERC-funded project (GLOSAT) will produce further ocean detail using marine air temperatures. Tim concluded by pointing out that updating series every month is not a simple routine operation. Many more land station series are being digitized and made available, and many more ship logbooks are being found and digitized. Matt Collins (University of Exeter) began by saying that climate modelling is now 100 years old, as Lewis Fry Richardson's attempt at a weather forecast was published in 1922. Although Richardson's forecast was a failure, use of the same data would have worked with an added data assimilation phase. Matt went through a history of modelling from the 1950s, highlighting work by Syukuro Manabe (who recently was jointly awarded the Nobel Prize for Physics) and the climate modelling predictions of Jim Hansen from 1988, which compare well with data up to 2021 if his scenario B forcing is used (which was closest to the actual greenhouse gas emissions). Matt emphasized the importance of ensembles of simulations and how these led to better model comparisons (coordinated by the Program for Climate Model Diagnosis and Intercomparison, PCMDI, in numerous Climate Model Intercomparison Projects, CMIP3, CMIP5 and CMIP6). PCMDI also independently compared different models against a standardized set of observational data. Matt concluded with two very important points: first, the improvements in computing with time seem to be levelling off, and second that the same comparisons through different model versions reveal several stubborn model biases, which are similar between different models and between later versions of the same models. Peter Stott (Met Office) introduced the Detection and Attribution (D&A) question. Greenhouse gases concentrations have risen and surface temperatures have also gone up, but is the latter related to the former? Peter showed the answer was clearly yes, highlighting the work of Ben Santer and Gabi Hergerl, who both worked with Klaus Hasselmann, who was jointly awarded the Nobel Prize for Physics with Manabe in 2021. Ben worked on the fingerprint of temperature change in the vertical (warming in the troposphere and cooling in the stratosphere), while Gabi worked on detecting signals (from climate models) in noisy observational data (not just temperature, but other variables such as precipitation and indices of extremes). The D&A chapter in IPCC Reports is always the most contentious and leads to the key sentences in an IPCC Summary for Policymakers. This has led to a backlash from climate science deniers, and personal attacks on the scientists involved. In the recent IPCC Sixth Assessment Report (AR6), the statement made was that human influences were unequivocal. Peter concluded with a discussion of event attribution, for example where the Siberian heatwave of January to June 2020 could not have occurred without Climate Change. Jason Lowe (Met Office) moved onto the Policy Advice given to UK Governments over 5-year periods since the Rio summit in 1992. This includes the setting up of the UN Framework Convention on Climate Change (UNFCCC) and the annual Conference of the Parties (COP) meetings up to COP26 last year in Glasgow that followed. Jason highlighted the COPs that achieved the most, and showed that emission reductions have been achieved by the UK, the EU and the US and Canada, but reductions are small, with much larger increases from China, India and the Rest of the World. The UNFCCC indirectly led to the UK Climate Change Act in 2008. Later two AVOID (Avoiding Dangerous Climate Change) programs have assessed UK achievements and what more needs to be done to further reduce emissions. He concluded by stating that science needs to focus on solutions and in narrowing uncertainties particularly with respect to the carbon cycle. COP26 pledges (e.g. phasing out the sale of petrol and diesel cars by 2030) could reduce temperature increases by 0.2–0.3 degC by 2050, but these do not get close to the 1.5 degC Paris aim of the overall temperature rise from the pre-industrial to 2050. Richard Betts (Met Office) then moved to adaptation with conclusions from the AR6 WG2 Report that was released a couple of weeks earlier. This report showed that all impacts of climate change across all continents and sectors assessed were adverse. There was no positive impact. This showed that emissions need to be halved by 2030 if we are to get below a 2 degC this century rise in temperature by 2100. Most of the AR6 WG2 conclusions are stark. Half the world's population in hotspots with respect to climate change are affected by poverty, poor governance and limited access to basic services. Improving food security has many adaptation options. There is potential for adaption by transforming cities – using engineering and nature-based approaches, but in some parts of the world maladaptation is happening. Richard emphasised two aspects at the end: (1) It is important not to rely on central estimates, but the potential for risk also needs to know about changes in variability, and (2) neither the UK nor the world is adapted to climate change. David Warrilow concluded by addressing whether the societal response to climate change has been adequate? David began with a slide of dates when key events happened such as the setting up of the IPCC in 1998 through to the Glasgow COP in 2021. He concluded along similar lines to Jason Lowe and Richard Betts that little has been achieved, except for some emissions reductions in Europe and North America. He mentioned several impediments such as fossil fuels being seen as being fundamental to economic growth, the US stance on the issue and until the Paris COP, the lack of long-term goals. He concluded optimistically, that there had been some impacts of policy in the West, renewable technology has greatly reduced in price, and the 2030 commitments from the Glasgow COP are much larger than earlier. Sir Brian Hoskins then led a brief discussion session that included Tim Osborn, John Mitchell, Jason Lowe and Keith Shine. Each picked a couple of points that they considered the most important. In the history of climate science context, John pointed to a number of events that helped climate model development at the Met Office and at UK Universities. First, the two worked together, not competitively, and the collaboration became more formal with time. Second, the Met Office worked with UK Government Departments (initially the Department of the Environment, Transport and the Regions in the 1980s, but the department names change regularly) which was novel at the time. The international involvement in the AMIP climate model comparisons (led by PCMDI) and IPCC created a unique environment that fostered collaboration not just within the UK, but across the world.