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Net anthropogenic emissions of carbon dioxide (CO2) must approach zero by mid-century (2050) in order to stabilize the global mean temperature at the level targeted by international efforts1-5. Yet continued expansion of fossil-fuel-burning energy infrastructure implies already 'committed' future CO2 emissions6-13. Here we use detailed datasets of existing fossil-fuel energy infrastructure in 2018 to estimate regional and sectoral patterns of committed CO2 emissions, the sensitivity of such emissions to assumed operating lifetimes and schedules, and the economic value of the associated infrastructure. We estimate that, if operated as historically, existing infrastructure will cumulatively emit about 658 gigatonnes of CO2 (with a range of 226 to 1,479 gigatonnes CO2, depending on the lifetimes and utilization rates assumed). More than half of these emissions are predicted to come from the electricity sector; infrastructure in China, the USA and the 28 member states of the European Union represents approximately 41 per cent, 9 per cent and 7 per cent of the total, respectively. If built, proposed power plants (planned, permitted or under construction) would emit roughly an extra 188 (range 37-427) gigatonnes CO2. Committed emissions from existing and proposed energy infrastructure (about 846 gigatonnes CO2) thus represent more than the entire carbon budget that remains if mean warming is to be limited to 1.5 degrees Celsius (°C) with a probability of 66 to 50 per cent (420-580 gigatonnes CO2)5, and perhaps two-thirds of the remaining carbon budget if mean warming is to be limited to less than 2 °C (1,170-1,500 gigatonnes CO2)5. The remaining carbon budget estimates are varied and nuanced14,15, and depend on the climate target and the availability of large-scale negative emissions16. Nevertheless, our estimates suggest that little or no new CO2-emitting infrastructure can be commissioned, and that existing infrastructure may need to be retired early (or be retrofitted with carbon capture and storage technology) in order to meet the Paris Agreement climate goals17. Given the asset value per tonne of committed emissions, we suggest that the most cost-effective premature infrastructure retirements will be in the electricity and industry sectors, if non-emitting alternatives are available and affordable4,18.

Net anthropogenic emissions of carbon dioxide (CO.sub.2) must approach zero by mid-century (2050) in order to stabilize the global mean temperature at the level targeted by international efforts.sup.1-5. Yet continued expansion of fossil-fuel-burning energy infrastructure implies already 'committed' future CO.sub.2 emissions.sup.6-13. Here we use detailed datasets of existing fossil-fuel energy infrastructure in 2018 to estimate regional and sectoral patterns of committed CO.sub.2 emissions, the sensitivity of such emissions to assumed operating lifetimes and schedules, and the economic value of the associated infrastructure. We estimate that, if operated as historically, existing infrastructure will cumulatively emit about 658 gigatonnes of CO.sub.2 (with a range of 226 to 1,479 gigatonnes CO.sub.2, depending on the lifetimes and utilization rates assumed). More than half of these emissions are predicted to come from the electricity sector; infrastructure in China, the USA and the 28 member states of the European Union represents approximately 41 per cent, 9 per cent and 7 per cent of the total, respectively. If built, proposed power plants (planned, permitted or under construction) would emit roughly an extra 188 (range 37-427) gigatonnes CO.sub.2. Committed emissions from existing and proposed energy infrastructure (about 846 gigatonnes CO.sub.2) thus represent more than the entire carbon budget that remains if mean warming is to be limited to 1.5 degrees Celsius (°C) with a probability of 66 to 50 per cent (420-580 gigatonnes CO.sub.2).sup.5, and perhaps two-thirds of the remaining carbon budget if mean warming is to be limited to less than 2 °C (1,170-1,500 gigatonnes CO.sub.2).sup.5. The remaining carbon budget estimates are varied and nuanced.sup.14,15, and depend on the climate target and the availability of large-scale negative emissions.sup.16. Nevertheless, our estimates suggest that little or no new CO.sub.2-emitting infrastructure can be commissioned, and that existing infrastructure may need to be retired early (or be retrofitted with carbon capture and storage technology) in order to meet the Paris Agreement climate goals.sup.17. Given the asset value per tonne of committed emissions, we suggest that the most cost-effective premature infrastructure retirements will be in the electricity and industry sectors, if non-emitting alternatives are available and affordable.sup.4,18. A comprehensive assessment of 'committed' carbon dioxide emissions--from existing and proposed fossil-fuel-based infrastructure--finds that these emissions may exceed the level required to keep global warming within 1.5 degrees Celsius., Author(s): Dan Tong [sup.1] [sup.2] , Qiang Zhang [sup.2] , Yixuan Zheng [sup.2] [sup.3] , Ken Caldeira [sup.3] , Christine Shearer [sup.4] , Chaopeng Hong [sup.1] , Yue Qin [sup.1] [...]

Climate models provide the principal means of projecting global warming over the remainder of the twenty-first century but modelled estimates of warming vary by a factor of approximately two even under the same radiative forcing scenarios. Across-model relationships between currently observable attributes of the climate system and the simulated magnitude of future warming have the potential to inform projections. Here we show that robust across-model relationships exist between the global spatial patterns of several fundamental attributes of Earths top-of-atmosphere energy budget and the magnitude of projected global warming. When we constrain the model projections with observations, we obtain greater means and narrower ranges of future global warming across the major radiative forcing scenarios, in general. In particular, we find that the observationally informed warming projection for the end of the twenty-first century for the steepest radiative forcing scenario is about 15 per cent warmer (+0.5 degrees Celsius) with a reduction of about a third in the two-standard-deviation spread (1.2 degrees Celsius) relative to the raw model projections reported by the Intergovernmental Panel on Climate Change. Our results suggest that achieving any given global temperature stabilization target will require steeper greenhouse gas emissions reductions than previously calculated., Author(s): Patrick T. Brown (corresponding author) [1]; Ken Caldeira [1] Many relevant impacts of global climate change are expected to scale with the change in global mean surface air temperature [...]

Author(s): Patrick T. Brown [sup.1] , Martin B. Stolpe [sup.2] , Ken Caldeira [sup.1] Author Affiliations:(1) Department of Global Ecology, Carnegie Institution for Science, Stanford, USA(2) Institute for Atmospheric and [...]

Approximately one-quarter of the anthropogenic carbon dioxide released into the atmosphere each year is absorbed by the global oceans, causing measurable declines in surface ocean pH, carbonate ion concentration ([C[O.sub.3.sup.2-]), [...]

Letter to the Editor, Author(s): Ken Caldeira, Ian McKay Author Affiliations: Contrails: tweaking flight altitude could be a climate win By our calculation, preventing most of the damaging impact of aircraft vapour trails (contrails) [...]

Author(s): Rebecca Albright (corresponding author) [1, 2]; Yuichiro Takeshita [1, 3]; David A. Koweek [1]; Aaron Ninokawa [4]; Kennedy Wolfe [5]; Tanya Rivlin [6, 7]; Yana Nebuchina [1]; Jordan Young [...]

Environmental conditions during the past 24 million years are thought to have been favourable for enhanced rates of atmospheric carbon dioxide drawdown by silicate chemical weathering (1-7). Proxy records indicate, however, that the Earth's atmospheric carbon dioxide concentrations did not fall below about 200-250 parts per million during this period (8). The stabilization of atmospheric carbon dioxide concentrations near this minimum value suggests that strong negative feedback mechanisms inhibited further drawdown of atmospheric carbon dioxide by high rates of global silicate rock weathering. Here we investigate one possible negative feedback mechanism, occurring under relatively low carbon dioxide concentrations and in warm climates, that is related to terrestrial plant productivity and its role in the decomposition of silicate minerals9-11. We use simulations of terrestrial and geochemical carbon cycles and available experimental evidence to show that vegetation activity in upland regions of active orogens was severely limited by near-starvation of carbon dioxide in combination with global warmth over this period. These conditions diminished biotic-driven silicate rock weathering and thereby attenuated an important long-term carbon dioxide sink. Although our modelling results are semi-quantitative and do not capture the full range of biogeochemical feedbacks that could influence the climate, our analysis indicates that the dynamic equilibrium between plants, climate and the geosphere probably buffered the minimum atmospheric carbon dioxide concentrations over the past 24 million years., Alkenone-based proxy records8 indicate that atmospheric carbon dioxide (C[O.sub.2]) concentrations ranged between 1,000 and 1,500 parts per million (p.p.m.) from about 45 to 34 million years (Myr) ago (the middle [...]

The United Nations (UN) has called for greenhouse gas concentration to be stabilized in its Convention on Climate Change, in order to prevent global warming. Stabilization will need cost-effective and innovative technology if economic growth is to continue, and this is true even if the productivity of primary energy is improved on a sustained basis. The lower the emission targets, the more carbon-emission-free power will be needed. There is a need for large investments in energy research due to the major challenge involved in infrastructure transition.

Carbon dioxide emission scenarios do not influence the global warming potential of CO2 with respect to other radioactive trace gases. Six scenarios are examined to indicate that atmospheric CO2 concentration is inversely proportional to the variation in climate. The sea absorbs less CO2 from the atmosphere due to increased concentrations of dissolved carbon in the sea's surface.

The warming of the Earth soon after it formed probably prevented the onset of an interminable glacial climate due to highly reflective carbon dioxide (CO2) clouds and the Sun's much less intense output of heat at the time. The suggestion that an early greenhouse effect stabilized the Earth's climate does not explain why the oceans failed to freeze before the greenhouse gases could accumulate. Paleoclimatic simulations indicate that Earth may have narrowly escaped being rendered uninhabitable by world-wide glaciation thanks to either internal heat or additional greenhouse gases.

The hypothesis that the rise of the Tibetan plateau helped to lower global temperatures by increasing the quantity of carbon dioxide(CO2)-absorbing silicate rock is questionable. The numerical data underlying this hypothesis are incomplete. Moreover, the implication that CO2 fluctuations are linked to geological weathering is unproven. However, the rebuttal view is that some carbon cycle models do relate to silicate and carbonate weathering. The hypothesis agrees well with the geological data.

Author(s): Ken Caldeira (corresponding author) [1]; Michael E. Wickett [2] Most carbon dioxide released into the atmosphere as a result of the burning of fossil fuels will eventually be absorbed [...]

The views of E.N. Parker on the potential impact on terrestrial climate, published with the paper on solar variability of M. Lockwood and others are inaccurate and out of line with Lockwood's evidence. Parker's suggestion that solar brightening causes an increase in carbon dioxide levels comparable with the expulsion of carbon dioxide from a warm carbonated drink is exaggerated.

Environmental conditions during the past 24 million years are thought to have been favourable for enhanced rates of atmospheric carbon dioxide drawdown by silicate chemical weathering. Proxy records indicate, however, that the Earth’s atmospheric carbon dioxide concentrations did not fall below about 200–250 parts per million during this period. The stabilization of atmospheric carbon dioxide concentrations near this minimum value suggests that strong negative feedback mechanisms inhibited further drawdown of atmospheric carbon dioxide by high rates of global silicate rock weathering. Here we investigate one possible negative feedback mechanism, occurring under relatively low carbon dioxide concentrations and in warm climates, that is related to terrestrial plant productivity and its role in the decomposition of silicate minerals. We use simulations of terrestrial and geochemical carbon cycles and available experimental evidence to show that vegetation activity in upland regions of active orogens was severely limited by near-starvation of carbon dioxide in combination with global warmth over this period. These conditions diminished biotic-driven silicate rock weathering and thereby attenuated an important long-term carbon dioxide sink. Although our modelling results are semi-quantitative and do not capture the full range of biogeochemical feedbacks that could influence the climate, our analysis indicates that the dynamic equilibrium between plants, climate and the geosphere probably buffered the minimum atmospheric carbon dioxide concentrations over the past 24 million years. [ABSTRACT FROM AUTHOR]