Ken Caldeira
Biographic Data
| ID | 6571754 |
|---|---|
| NAME | Ken Caldeira |
| GIVEN NAMES | Ken |
| FAMILY NAME | Caldeira |
| SIGNATURE | CALDEIRA K |
| AFFILIATIONS | Carnegie Institution for Science |
| ORCID | 0000-0002-4591-643X |
| VERIFIED | Yes |
| TOTAL WORKS | 43 |
| TOTAL CITATIONS | 4 |
| AUTHOR COUNT | 43 |
| EDITOR COUNT | 0 |
| FIRST PUBLICATION YEAR | 2007 |
| LATEST PUBLICATION YEAR | 2025 |
| H-INDEX | 1 |
Trade risks to energy security in net-zero emissions energy scenarios
Economic development, air conditioning and adaptation to warming
Rising global temperatures increase the potential for heat-related adverse impacts, while economic growth, by enabling greater adoption of air conditioning, can help reduce them. This makes it unclear in which countries the net effect will lead to a worsening or easing of these potential impacts as the climate and economies change. We define a Cooling Deficit Index as the product of cooling degree days and the fraction of the population without a…
Rate of global warming projected to decline under current policy
The value of reducing the Green Premium: Cost-saving innovation, emissions abatement, and climate goals
Carbon-emitting technologies often cost less than carbon-emission-free alternatives; this difference in cost is known as the Green Premium. Innovations that decrease the Green Premium contribute to achieving climate goals, but a conceptual framework to quantify that contribution has been lacking. Here, we devise a framework to translate reductions in the Green Premium into equivalent reductions in carbon emissions. We introduce a new integrated a…
Move up or move over: Mapping opportunities for climate adaptation in Pakistan’s Indus plains
The 2022 Indus floods in Pakistan underscore the urgency of adapting to more frequent and severe natural disasters in a warming world. Post-disaster reconstruction offers a chance to built-in adaptation measures, but identifying feasible and cost-effective adaptation options is challenging, especially in data-scarce regions. Here we employ a high-resolution rapid assessment of flood stages combined with demographic data to identify adaptation opp…
Food without agriculture
Efforts to make food systems more sustainable have emphasized reducing adverse environmental impacts of agriculture. In contrast, chemical and biological processes that could produce food without agriculture have received comparatively little attention or resources. Although there is a possibility that someday a wide array of attractive foods could be produced chemosynthetically, here we show that dietary fats could be synthesized with 1.5 g CO 2…
Guiding the deployment of electric vehicles in the developing world
Contrasting climate and carbon-cycle consequences of fossil-fuel use versus deforestation disturbance
Carbon dioxide emissions from deforestation disturbance (e.g. clear-cutting, forest fires) are in the same units as carbon dioxide emissions from fossil fuels. However, if the forest is allowed to regrow, there is a large difference between climate effects of that forest disturbance and climate effects of fossil CO 2 . In this study, using a set of idealized global climate-carbon model simulations with equal amounts of CO 2 emissions, we show tha…
Climate effects of aerosols reduce economic inequality
Climate effects of China’s efforts to improve its air quality
Facing severe air pollution issues, China has implemented a series of clean air policies aimed to improve the country’s air quality. These policies largely focused on reducing emissions of major air pollutants such as sulfur dioxide (SO 2 ) and primary aerosols. However, changes in such pollution also affect radiative forcing. To understand the climate consequences of these clean air actions in China, we evaluate the near-equilibrium climate resp…
Balancing climate and development goals
Decarbonizing the energy system is a major challenge facing the richest countries, whereas provision of energy services is a major challenge facing the poorest countries. What would be the climate consequences if only richer countries focus on decarbonization, and only poorer countries focus on provision of energy services? To address this question, we create future scenarios in which carbon dioxide (CO 2 ) emissions increase according to a histo…
Committed emissions from existing energy infrastructure jeopardize 1.5 °C climate target
The impact of climate change on fertility
We examine the potential for climate change to impact fertility via adaptations in human behavior. We start by discussing a wide range of economic channels through which climate change might impact fertility, including sectoral reallocation, the gender wage gap, longevity, and child mortality. Then, we build a quantitative model that combines standard economic-demographic theory with existing estimates of the economic consequences of climate chan…
Net-zero emissions energy systems
Path to zero carbon emissions Models show that to avert dangerous levels of climate change, global carbon dioxide emissions must fall to zero later this century. Most of these emissions arise from energy use. Davis et al. review what it would take to achieve decarbonization of the energy system. Some parts of the energy system are particularly difficult to decarbonize, including aviation, long-distance transport, steel and cement production, and …
Will the use of a carbon tax for revenue generation produce an incentive to continue carbon emissions
Integrated assessment models are commonly used to generate optimal carbon prices based on an objective function that maximizes social welfare. Such models typically project an initially low carbon price that increases with time. This framework does not reflect the incentives of decision makers who are responsible for generating tax revenue. If a rising carbon price is to result in near-zero emissions, it must ultimately result in near-zero carbon…
Quantifying expert consensus against the existence of a secret, large-scale atmospheric spraying program
Nearly 17% of people in an international survey said they believed the existence of a secret large-scale atmospheric program (SLAP) to be true or partly true. SLAP is commonly referred to as ‘chemtrails’ or ‘covert geoengineering’, and has led to a number of websites purported to show evidence of widespread chemical spraying linked to negative impacts on human health and the environment. To address these claims, we surveyed two groups of experts—…
ERL and the impact of small groups of authors
Evidence from the 100-most cited papers ever published in ERL indicates the disproportionately large scientific impact of small groups of authors. The median number of authors on these 100 most-cited papers was 3.5, and 72 out of the 100 most cited papers had 5 or fewer authors. This indicates that small groups of authors often produce the work with the greatest impact, even in an inter-disciplinary setting. This suggests that it may be wise to i…
Adapting to rates versus amounts of climate change: A case of adaptation to sea-level rise
Adaptation is the process of adjusting to climate change in order to moderate harm or exploit beneficial opportunities associated with it. Most adaptation strategies are designed to adjust to a new climate state. However, despite our best efforts to curtail greenhouse gas emissions, climate is likely to continue changing far into the future. Here, we show how considering rates of change affects the projected optimal adaptation strategy. We ground…
Why must a solar forcing be larger than a CO 2 forcing to cause the same global mean surface temperature change
Many previous studies have shown that a solar forcing must be greater than a CO 2 forcing to cause the same global mean surface temperature change but a process-based mechanistic explanation is lacking in the literature. In this study, we investigate the physical mechanisms responsible for the lower efficacy of solar forcing compared to an equivalent CO 2 forcing. Radiative forcing is estimated using the Gregory method that regresses top-of-atmos…
Impacts of ocean albedo alteration on Arctic sea ice restoration and Northern Hemisphere climate
The Arctic Ocean is expected to transition into a seasonally ice-free state by mid-century, enhancing Arctic warming and leading to substantial ecological and socio-economic challenges across the Arctic region. It has been proposed that artificially increasing high latitude ocean albedo could restore sea ice, but the climate impacts of such a strategy have not been previously explored. Motivated by this, we investigate the impacts of idealized hi…
Atmospheric consequences of disruption of the ocean thermocline
Technologies utilizing vertical ocean pipes have been proposed as a means to avoid global warming, either by providing a source of clean energy, increasing ocean carbon uptake, or storing thermal energy in the deep ocean. However, increased vertical transport of water has the capacity to drastically alter the ocean thermocline. To help bound potential climate consequences of these activities, we perform a set of simulations involving idealized di…
Maximum warming occurs about one decade after a carbon dioxide emission
It is known that carbon dioxide emissions cause the Earth to warm, but no previous study has focused on examining how long it takes to reach maximum warming following a particular CO _2 emission. Using conjoined results of carbon-cycle and physical-climate model intercomparison projects (Taylor et al 2012 , Joos et al 2013 ), we find the median time between an emission and maximum warming is 10.1 years, with a 90% probability range of 6.6–30.7 ye…
CH 4 and N 2 O emissions embodied in international trade of meat
Although previous studies have quantified carbon dioxide emissions embodied in products traded internationally, there has been limited attention to other greenhouse gases such as methane (CH4) and nitrous oxide (N2O). Following IPCC guidelines, we estimate non-CO2 emissions from beef, pork and chicken produced in 237 countries over the period 1990–2010, and assign these emissions to the country where the meat is ultimately consumed. We find that,…
Key factors for assessing climate benefits of natural gas versus coal electricity generation
Assessing potential climate effects of natural gas versus coal electricity generation is complicated by the large number of factors reported in life cycle assessment studies, compounded by the large number of proposed climate metrics. Thus, there is a need to identify the key factors affecting the climate effects of natural gas versus coal electricity production, and to present these climate effects in as clear and transparent a way as possible. …
Risks to coral reefs from ocean carbonate chemistry changes in recent earth system model projections
Coral reefs are among the most biodiverse ecosystems in the world. Today they are threatened by numerous stressors, including warming ocean waters and coastal pollution. Here we focus on the implications of ocean acidification for the open ocean chemistry surrounding coral reefs, as estimated from earth system models participating in the Coupled Model Intercomparison Project, Phase 5 (CMIP5). We project risks to reefs in the context of three pote…
Coupled climate–carbon simulations indicate minor global effects of wars and epidemics on atmospheric CO 2 between ad 800 and 1850
Historic events such as wars and epidemics have been suggested as explanation for decreases in atmospheric CO 2 reconstructed from ice cores because of their potential to take up carbon in forests regrowing on abandoned agricultural land. Here, we use a coupled climate–carbon cycle model to assess the carbon and climate effects of the Mongol invasion (~1200 to ~1380), the Black Death (~1347 to ~1400), the conquest of the Americas (~1519 to ~1700)…
Food without agriculture
Efforts to make food systems more sustainable have emphasized reducing adverse environmental impacts of agriculture. In contrast, chemical and biological processes that could produce food without agriculture have received comparatively little attention or resources. Although there is a possibility that someday a wide array of attractive foods could be produced chemosynthetically, here we show that dietary fats could be synthesized with 1.5 g CO 2…
Combined climate and carbon-cycle effects of large-scale deforestation
The prevention of deforestation and promotion of afforestation have often been cited as strategies to slow global warming. Deforestation releases CO 2 to the atmosphere, which exerts a warming influence on Earth's climate. However, biophysical effects of deforestation, which include changes in land surface albedo, evapotranspiration, and cloud cover also affect climate. Here we present results from several large-scale deforestation experiments pe…
Stabilizing climate requires near‐zero emissions
Current international climate mitigation efforts aim to stabilize levels of greenhouse gases in the atmosphere. However, human‐induced climate warming will continue for many centuries, even after atmospheric CO 2 levels are stabilized. In this paper, we assess the CO 2 emissions requirements for global temperature stabilization within the next several centuries, using an Earth system model of intermediate complexity. We show first that a single p…
Protecting climate with forests
Policies for climate mitigation on land rarely acknowledge biophysical factors, such as reflectivity, evaporation, and surface roughness. Yet such factors can alter temperatures much more than carbon sequestration does, and often in a conflicting way. We outline a framework for examining biophysical factors in mitigation policies and provide some best-practice recommendations based on that framework. Tropical projects—avoided deforestation, fores…
Atmospheric Lifetime of Fossil Fuel Carbon Dioxide
CO 2 released from combustion of fossil fuels equilibrates among the various carbon reservoirs of the atmosphere, the ocean, and the terrestrial biosphere on timescales of a few centuries. However, a sizeable fraction of the CO 2 remains in the atmosphere, awaiting a return to the solid earth by much slower weathering processes and deposition of CaCO 3 . Common measures of the atmospheric lifetime of CO 2 , including the e-folding time scale, dis…
Consumption-based accounting of CO 2 emissions
CO 2 emissions from the burning of fossil fuels are the primary cause of global warming. Much attention has been focused on the CO 2 directly emitted by each country, but relatively little attention has been paid to the amount of emissions associated with the consumption of goods and services in each country. Consumption-based accounting of CO 2 emissions differs from traditional, production-based inventories because of imports and exports of goo…
Future CO 2 Emissions and Climate Change from Existing Energy Infrastructure
What We're In For What would our climate future look like if we stopped building any new infrastructure that used fossil fuels? Davis et al. (p. 1330 ; see the Perspective by Hoffert ) made the assumption that all existing infrastructure will be used until the end of its lifetime, after which it will be replaced by infrastructure that does not produce CO 2 . They then calculated the amount of additional CO 2 that will be added to the atmosphere. …
Atmospheric carbon dioxide removal: Long-term consequences and commitment
Carbon capture from ambient air has been proposed as a mitigation strategy to counteract anthropogenic climate change. We use an Earth system model to investigate the response of the coupled climate–carbon system to an instantaneous removal of all anthropogenic CO2 from the atmosphere. In our extreme and idealized simulations, anthropogenic CO2 emissions are halted and all anthropogenic CO2 is removed from the atmosphere at year 2050 under the IP…
Geoengineering as an optimization problem
There is increasing evidence that Earth’s climate is currently warming, primarily due to emissions of greenhouse gases from human activities, and Earth has been projected to continue warming throughout this century. Scientists have begun to investigate the potential for geoengineering options for reducing surface temperatures and whether such options could possibly contribute to environmental risk reduction. One proposed method involves deliberat…
The supply chain of CO 2 emissions
CO 2 emissions from the burning of fossil fuels are conventionally attributed to the country where the emissions are produced (i.e., where the fuels are burned). However, these production-based accounts represent a single point in the value chain of fossil fuels, which may have been extracted elsewhere and may be used to provide goods or services to consumers elsewhere. We present a consistent set of carbon inventories that spans the full supply …
Climate forcing and response to idealized changes in surface latent and sensible heat
Land use and land cover changes affect the partitioning of latent and sensible heat, which impacts the broader climate system. Increased latent heat flux to the atmosphere has a local cooling influence known as `evaporative cooling', but this energy will be released back to the atmosphere wherever the water condenses. However, the extent to which local evaporative cooling provides a global cooling influence has not been well characterized. Here, …
Coupled climate–carbon simulations indicate minor global effects of wars and epidemics on atmospheric CO 2 between ad 800 and 1850
Historic events such as wars and epidemics have been suggested as explanation for decreases in atmospheric CO 2 reconstructed from ice cores because of their potential to take up carbon in forests regrowing on abandoned agricultural land. Here, we use a coupled climate–carbon cycle model to assess the carbon and climate effects of the Mongol invasion (~1200 to ~1380), the Black Death (~1347 to ~1400), the conquest of the Americas (~1519 to ~1700)…
Climate response to changes in atmospheric carbon dioxide and solar irradiance on the time scale of days to weeks
Recent studies show that fast climate response on time scales of less than a month can have important implications for long-term climate change. In this study, we investigate climate response on the time scale of days to weeks to a step-function quadrupling of atmospheric CO _2 and contrast this with the response to a 4% increase in solar irradiance. Our simulations show that significant climate effects occur within days of a stepwise increase in…
Greenhouse gases, climate change and the transition from coal to low-carbon electricity
A transition from the global system of coal-based electricity generation to low-greenhouse-gas-emission energy technologies is required to mitigate climate change in the long term. The use of current infrastructure to build this new low-emission system necessitates additional emissions of greenhouse gases, and the coal-based infrastructure will continue to emit substantial amounts of greenhouse gases as it is phased out. Furthermore, ocean therma…
Attribution of atmospheric CO 2 and temperature increases to regions: Importance of preindustrial land use change
The historical contribution of each country to today’s observed atmospheric CO _2 excess and higher temperatures has become a basis for discussions around burden-sharing of greenhouse gas reduction commitments in political negotiations. However, the accounting methods have considered greenhouse gas emissions only during the industrial era, neglecting the fact that land use changes (LUC) have caused emissions long before the Industrial Revolution.…
Ecosystem Impacts of Geoengineering: A Review for Developing a Science Plan
Risks to coral reefs from ocean carbonate chemistry changes in recent earth system model projections
Coral reefs are among the most biodiverse ecosystems in the world. Today they are threatened by numerous stressors, including warming ocean waters and coastal pollution. Here we focus on the implications of ocean acidification for the open ocean chemistry surrounding coral reefs, as estimated from earth system models participating in the Coupled Model Intercomparison Project, Phase 5 (CMIP5). We project risks to reefs in the context of three pote…
Rethinking wedges
Stabilizing CO _2 emissions at current levels for fifty years is not consistent with either an atmospheric CO _2 concentration below 500 ppm or global temperature increases below 2 °C. Accepting these targets, solving the climate problem requires that emissions peak and decline in the next few decades, and ultimately fall to near zero. Phasing out emissions over 50 years could be achieved by deploying on the order of 19 ‘wedges’, each of which ra…
Strategic incentives for climate geoengineering coalitions to exclude broad participation
Solar geoengineering is the deliberate reduction in the absorption of incoming solar radiation by the Earth’s climate system with the aim of reducing impacts of anthropogenic climate change. Climate model simulations project a diversity of regional outcomes that vary with the amount of solar geoengineering deployed. It is unlikely that a single small actor could implement and sustain global-scale geoengineering that harms much of the world withou…
Projections of the pace of warming following an abrupt increase in atmospheric carbon dioxide concentration
The temperature response of atmosphere–ocean climate models is analyzed based on atmospheric CO _2 step-function-change simulations submitted to phase 5 of the Coupled Model Intercomparison Project (CMIP5). From these simulations and a control simulation, we estimate adjusted radiative forcing, the climate feedback parameter, and effective climate system thermal inertia, and we show that these results can be used to predict the temperature respon…
Maximum warming occurs about one decade after a carbon dioxide emission
It is known that carbon dioxide emissions cause the Earth to warm, but no previous study has focused on examining how long it takes to reach maximum warming following a particular CO _2 emission. Using conjoined results of carbon-cycle and physical-climate model intercomparison projects (Taylor et al 2012 , Joos et al 2013 ), we find the median time between an emission and maximum warming is 10.1 years, with a 90% probability range of 6.6–30.7 ye…
CH 4 and N 2 O emissions embodied in international trade of meat
Although previous studies have quantified carbon dioxide emissions embodied in products traded internationally, there has been limited attention to other greenhouse gases such as methane (CH4) and nitrous oxide (N2O). Following IPCC guidelines, we estimate non-CO2 emissions from beef, pork and chicken produced in 237 countries over the period 1990–2010, and assign these emissions to the country where the meat is ultimately consumed. We find that,…
Key factors for assessing climate benefits of natural gas versus coal electricity generation
Assessing potential climate effects of natural gas versus coal electricity generation is complicated by the large number of factors reported in life cycle assessment studies, compounded by the large number of proposed climate metrics. Thus, there is a need to identify the key factors affecting the climate effects of natural gas versus coal electricity production, and to present these climate effects in as clear and transparent a way as possible. …
Impacts of ocean albedo alteration on Arctic sea ice restoration and Northern Hemisphere climate
The Arctic Ocean is expected to transition into a seasonally ice-free state by mid-century, enhancing Arctic warming and leading to substantial ecological and socio-economic challenges across the Arctic region. It has been proposed that artificially increasing high latitude ocean albedo could restore sea ice, but the climate impacts of such a strategy have not been previously explored. Motivated by this, we investigate the impacts of idealized hi…
Atmospheric consequences of disruption of the ocean thermocline
Technologies utilizing vertical ocean pipes have been proposed as a means to avoid global warming, either by providing a source of clean energy, increasing ocean carbon uptake, or storing thermal energy in the deep ocean. However, increased vertical transport of water has the capacity to drastically alter the ocean thermocline. To help bound potential climate consequences of these activities, we perform a set of simulations involving idealized di…
Quantifying expert consensus against the existence of a secret, large-scale atmospheric spraying program
Nearly 17% of people in an international survey said they believed the existence of a secret large-scale atmospheric program (SLAP) to be true or partly true. SLAP is commonly referred to as ‘chemtrails’ or ‘covert geoengineering’, and has led to a number of websites purported to show evidence of widespread chemical spraying linked to negative impacts on human health and the environment. To address these claims, we surveyed two groups of experts—…
Environmental Science (39 works) · Climate change (32 works) · Greenhouse gas (26 works) · Geography (22 works) · Climatology (20 works) · Climate Change Policy and Economics (19 works) · Global warming (19 works) · Economics (18 works) · Natural resource economics (18 works) · Atmospheric sciences (17 works)