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Last Monday, I was invited to speak on the occasion of the 100 years anniversary of the International Union of Geodesy and Geophysics @theIUGG @UNESCO.
@theIUGG @UNESCO It was an opportunity to reflect on a success story, a failure story, and a transformation story, looking both backwards and forward.
@theIUGG @UNESCO Looking backwards, it is extremely impressive to consider the climate science achievements of the past century.
@theIUGG @UNESCO Thanks to the deployment, strengthening, and improvement of observation techniques, we now have the capacity to monitor key aspects of the climate system :
@theIUGG @UNESCO changes in the Earth's energy budget, changes in global and regional climate, from the top of the atmosphere to the depths of oceans.
@theIUGG @UNESCO This has been achieved thanks to technological progress, logistical progress, international cooperation, including in situ monitoring, and since the 1970s, remote sensing from space.
@theIUGG @UNESCO We also benefit from impressive progress in process-based understanding, theoretical developments, as well as the revolution of numerical modelling.
@theIUGG @UNESCO Starting from weather forecast, which combines the skills of monitoring, atmospheric modelling and data assimulation, the field of climate modelling has expanded since the second half of the 20th century.
@theIUGG @UNESCO Climate and Earth system models play a key role to understand how the climate system operates, why it has changed in the past, and what are physically plausible future climate changes, depending on our actions.
@theIUGG @UNESCO World media have recently celebrated the 50th anniversary of the 1st footstep of a human being on the Moon as a major achievement.
@theIUGG @UNESCO No such echo has been given to the 40th anniversary of the Charney report, which was one of the first scientific assessments of the role of greenhouse gases emitted as a result of human activities on global climate.
@theIUGG @UNESCO This report estimated the range of climate sensitivity - a metrics which measures the most probable warming at the Earth's surface resulting from x2 the atmospheric CO2 concentration above pre-industrial levels, to be 3°C with a range of plus or minus 1.5°C.
@theIUGG @UNESCO So far, this range has been supported by more evidence from paleoclimate, observations, theory and much more sophisticated numerical climate models.
@theIUGG @UNESCO Given the implication of climate sensitivity for future risks and our margin of action, it is more urgent then ever to better constrain the range of climate sensitivity, through breakthroughs in basic climate research.
@theIUGG @UNESCO My own research has been focused on past climate, and driven by curiosity.
@theIUGG @UNESCO Along the last century, new knowledge has also been produced thanks to the use of natural archives ("retroactive observations") to characterize and understand past climate variations.
@theIUGG @UNESCO Past climates allow us to characterize and understand the full range of variability of the Earth's climate. They give us acess to a diversity of "natural experiments" on the Earth's climate, unveil the timescales of feedbacks and responses to geological or astronomical forcings.
@theIUGG @UNESCO Past climates also provide benchmarks against which we can test the robustness of climate and Earth system models. The fact that these models can correctly simulate the broad features of extreme climate states of the geological history, from Eocene warmth to ice ages, ...
@theIUGG @UNESCO the response to astronomical or volcanic forcing, and the characteristics of climate variability during the historical period is key for our confidence in their projections.
@theIUGG @UNESCO Our knowledge of past climates demonstrates the unprecedented perturbation already caused by human activities on the atmospheric composition, altering the Earth's energy budget, trapping heat. Welcome to the Anthropocene!
@theIUGG @UNESCO Last week, new studies have confirmed that the current 1°C rise of global mean surface temperature (since 1850-1900) is larger, faster, and more globally synchronous than at any other time of the past 2 thousand years.
@theIUGG @UNESCO Our best estimate is that 100% (plus or minus 20%) of this warming is due to the consequences of human activities. We already see the reality of this changing climate with trends and changes in extremes which affect ecosystems and livelihoods everywhere.
@theIUGG @UNESCO To finish these reflections on a success story of knowledge developments, I stress that the patterns of what has been observed in the last 30 years (warming of land > oceans, increased ocean heat content, Arctic amplification, intensified heat waves or extreme rainfall events)...
@theIUGG @UNESCO had been anticipated by the first ocean-atmosphere simulations published 30 years ago as well as the ensemble of projections starting in 2005.
@theIUGG @UNESCO With more than 20,000 peer-review publications with the keyword "climate change", relevant knowledge production from all disciplines is accelerating.
@theIUGG @UNESCO Part of this increase in the number of papers results from the pressure to publish, the expansion of predatory journals which are major challenges for the rigor of science and its credibility.
@theIUGG @UNESCO But most of the increase reflects the broad development of climate change sciences, including understanding impacts and risks, exploring options for risk management and enhancing resilience,
@theIUGG @UNESCO links with sustainability, preserving ecosystems and improving human well-being while reducing greenhouse gas emissions towards carbon neutrality, in all sectors, in all regions.
@theIUGG @UNESCO With more than 20,000 peer-review publications/year on this topic, more than ever, we need internationally coordinated efforts to assess the state of knowledge, from the critical examination the scientific literature.
@theIUGG @UNESCO This is the mandate of @IPCC_CH, which has celebrated its 30th anniversary last year, and is currently producing herculean efforts to deliver a set of reports within its Sixth Assessment cycle.
@theIUGG @UNESCO @IPCC_CH Last year, we released the #SR15 Special Report on global warming of 1.5°C. It is the most integrated assessment across disciplines to date.
@theIUGG @UNESCO @IPCC_CH At the current rate of warming, 0.2°C more per decade, global warming will reach 1.5°C between around 2030 and 2050 - when our children are our age.
@theIUGG @UNESCO @IPCC_CH This report illustrates how much every half a degree, every fraction of warming matters in terms of future climate-related impacts and risks.
@theIUGG @UNESCO @IPCC_CH It shows that for the preservation of healthy ecosystems, and for health, livelihoods, water supply, food secury, human security and economic development, there are clear benefits to limit global warming at 1.5°C compared to 2°C or more.
@theIUGG @UNESCO @IPCC_CH Risks are disproportionately higher in some regions, such as drylands, small island developing states, least developed countries, or the Arctic. Limited warming to 1.5°C compared to 2°C would avoid exposing several hundred million people susceptible to poverty to climate risks.
@theIUGG @UNESCO @IPCC_CH Major adaptation efforts are needed to manage risks, even for 1.5°C global warming.
@theIUGG @UNESCO @IPCC_CH This report also illustrates how much every year matters in terms of greenhouse gas emissions. Due to the cumulative effect of CO2, stabilizing global warming can only be achieved by sharp reductions in emissions to reach net zero as soon as possible.
@theIUGG @UNESCO @IPCC_CH It also implies to reduce the net warming effect on climate of other emissions, and reducing emissions of compounds that also cause air pollution would have immediate benefits for air quality and health.
@theIUGG @UNESCO @IPCC_CH If pedges from governements expressed in 2015 under the Paris Agreement are realized by 2025-2030, global greenhouse gas emissions would continue to increase until 2030. The current level of ambition would lead to global warming of 3°C or more by 2100.
@theIUGG @UNESCO @IPCC_CH Limiting gobal warming to 2°C would imply to reduce global CO2 emissions by 25% by 2030 and reach net zero by around 2070. For 1.5°C it would imply to reduce global CO2 emissions by 50% by 2030 and reach net zero by around 2050.
@theIUGG @UNESCO @IPCC_CH It would require rapid, far-reaching and unprecedented transitions in energy, land use, urban, industry and infrastructure systems, using a range of technologies and behaviour change. With more than 40 billion tons CO2 emitted per year, every year matters.
@theIUGG @UNESCO @IPCC_CH Finally, this report shows how much every choice matters. It builds on the intersections between climate change impacts and risks, options for adaptation, options for mitigation, and sustainable development goals.
@theIUGG @UNESCO @IPCC_CH By using this multi-dimensional analysis, it shows how ethical, fair and just transitions can be designed.
@theIUGG @UNESCO @IPCC_CH Different pathways have different synergies and trade-offs with sustainable development goals. In each context, a careful mix of measures to adapt to climate change and reduce emissions can help achieve these goals through low carbon, climate resilient development pathways.
@theIUGG @UNESCO @IPCC_CH Our assessment shows that, at the global scale, the highest co-benefits are identified in pathways with low energy demand, low consumption of non renewable material, and healty diets which reduce pressure on land & food system emissions.
@theIUGG @UNESCO @IPCC_CH Every fraction of warming, every year, every choice matters. I would also like to reflect on a failure story.
@theIUGG @UNESCO @IPCC_CH Despite decades of new knowledge development confirming that we are causing global climate change, including 30 years of IPCC assessments, global emissions of most greenhouse gases keep rising.
@theIUGG @UNESCO @IPCC_CH It sometimes looks like the unfolding of a Greek tragedy, where we see happening what had been anticipated decades ago by climate and Earth system modelling.
@theIUGG @UNESCO @IPCC_CH The small window of opportunity to limit global warming at low levels of closing fast with rising or stagnating emissions.
@theIUGG @UNESCO @IPCC_CH Failure to act at scale increases the burden on younger generations who will have to face the consequences of committed warming, potential irreversible loss of ecosystems, increasing crisis management, and most costly, difficult and risky options to manage risks.
@theIUGG @UNESCO @IPCC_CH Climate change literacy remains low amongst decision makers and the general public. Our science is not always part of school and university curricula. Climate literacy is not part of international benchmarking of education programmes and universities.
@theIUGG @UNESCO @IPCC_CH We are facing merchants of doubt, very efficient to use media to spread disinformation on the reality of climate change, its causes, and response options. Sometimes, scientists from other fields have been the most active to attack climate science and spread denial.
@theIUGG @UNESCO @IPCC_CH More and more people around the world are using social media to have access to information. The voice of science on social media is weak.
@theIUGG @UNESCO @IPCC_CH There are great stories to be deconstructed. The story which denies the evidence that our activities have profoundly disrupted atmospheric composition and climate, the evidence of growing impacts and further risks with more warming.
@theIUGG @UNESCO @IPCC_CH The story that governments, informed by the scientific community, will bravely make the decisions necessary for the long-term common good.
@theIUGG @UNESCO @IPCC_CH The story of fatalism and powerlessness, which plays on fears of committed, irreversible changes and on the inability of decision-makers to act at the scale of the issues at stake.
@theIUGG @UNESCO @IPCC_CH We must deconstruct these stories, and show how to deploy all levers of action available now, at all scales, wisely, collectively, and design solutions that can be deployed tomorrow through research and innovation.
@theIUGG @UNESCO @IPCC_CH Improved monitoring, understand and modelling of the Earth system is part of these solutions. Climate services, providing climate information relevant for decision making (with uncertainties of projections), at regional and sectoral scale, are also part of solutions.
@theIUGG @UNESCO @IPCC_CH We need science to be more easily accessible to everyone. Publications should be available to all, as a fair return to the support of citizen for science through their tax.
@theIUGG @UNESCO @IPCC_CH We need to support scientists so that they are trained to engage in social media, participatory approaches, and recognize these activities to be part of their jobs.
@theIUGG @UNESCO @IPCC_CH We need new mindsets with solid understanding of climate change, risks, and solutions. We need to support the integration of research activities, at the interface between disciplines, including social sciences, and to better understand nature based solutions
@theIUGG @UNESCO @IPCC_CH We need to build bridges between the academic world, practioners, engineers

@theIUGG @UNESCO @IPCC_CH We need to empower our students, young people, so that they understand climate science, and how to act in support of sustainability.
@theIUGG @UNESCO @IPCC_CH We need to work with cities where our research centers & universities are located, in order to provide a science background to facilitate transitions where we live.
@theIUGG @UNESCO @IPCC_CH We need to learn what are the needs of society, and develop new approaches for the co-design and co-production of knowledge.
@theIUGG @UNESCO @IPCC_CH Scientists are also sometimes the worse examples of cognitive dissonance, working on climate change while travelling by plane around the world to attend meetings. We need to reflect on our own practices.
@theIUGG @UNESCO @IPCC_CH How can we deploy pathways to reduce emissions associated with our research, while producing basic knowledge breakthroughs and knowledge supporting societal transformations?
@theIUGG @UNESCO @IPCC_CH How can we better use solutions of the 21st century such as videoconferencing to stimulate intellectual exchanges, cooperation, emulation, capacity building in all countries?

Let us look forward now.
@theIUGG @UNESCO @IPCC_CH Ice cores from Antarctica are extraordinary time machines which I used for my own research. With Antarctic scientists from various research areas, we tried to reflect on storylines for future changes in the Antarctic region by 2070.
@theIUGG @UNESCO @IPCC_CH In a century from now, by 2119, will we have preserved Antarctica as an area of science, cooperation and peace?
@theIUGG @UNESCO @IPCC_CH What will be the state of the (remains of the) cryosphere, the state of climate, the state of biodiversity, the state of humanity in 2119?
@theIUGG @UNESCO @IPCC_CH Will we have improved Earth system monitoring, early warming systems, seasonal and decadal predictions, near term and long term projections to build resilience and manage risks?
@theIUGG @UNESCO @IPCC_CH Will we have managed to reduce greenhouse gas emissions and to improve well-being for all, leaving no-one behind, through technological, frugal and social innovation?
@theIUGG @UNESCO @IPCC_CH Will we have managed to use science, technology and wisdom for human progress?
@theIUGG @UNESCO @IPCC_CH All this will depend on our actions in the coming years and decades. My last slide also shows the warming stripes of my first slide, along different shared socio-economic pathways, with different patterns of greenhouse gas emissions, and different choices.
@theIUGG @UNESCO @IPCC_CH As scientists, we must claim to carry the voice of science, share science with everyone, to put science at the service of the transformations of our societies, because we must act, in a lucid and responsible way, for the greatest challenge that we must face together.
@theIUGG @UNESCO @IPCC_CH - this was an attempt to convert a 20 mn talk to a twitter thread... sorry for my too long sentences! Waiting for comments and thoughts on climate science and society at the occasion of the 100th anniversary of @theIUGG, looking backward and forward...
@theIUGG @UNESCO @IPCC_CH (sorry, pledges, not pedges 😉)
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