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 Earth's 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.
Consumption-based accounting of CO₂ emissions Davis, Steven J; Caldeira, Ken
Proceedings of the National Academy of Sciences - PNAS,
03/2010, Letnik:
107, Številka:
12
Journal Article
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CO₂ emissions from the burning of fossil fuels are the primary cause of global warming. Much attention has been focused on the CO₂ 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 CO₂ emissions differs from traditional, production-based inventories because of imports and exports of goods and services that, either directly or indirectly, involve CO₂ emissions. Here, using the latest available data, we present a global consumption-based CO₂ emissions inventory and calculations of associated consumption-based energy and carbon intensities. We find that, in 2004, 23% of global CO₂ emissions, or 6.2 gigatonnes CO₂, were traded internationally, primarily as exports from China and other emerging markets to consumers in developed countries. In some wealthy countries, including Switzerland, Sweden, Austria, the United Kingdom, and France, >30% of consumption-based emissions were imported, with net imports to many Europeans of >4 tons CO₂ per person in 2004. Net import of emissions to the United States in the same year was somewhat less: 10.8% of total consumption-based emissions and 2.4 tons CO₂ per person. In contrast, 22.5% of the emissions produced in China in 2004 were exported, on net, to consumers elsewhere. Consumption-based accounting of CO₂ emissions demonstrates the potential for international carbon leakage. Sharing responsibility for emissions among producers and consumers could facilitate international agreement on global climate policy that is now hindered by concerns over the regional and historical inequity of emissions.
Climate change is expected to decrease heating demand and increase cooling demand for buildings and affect outdoor thermal comfort. Here, we project changes in residential heating degree-days (HDD) ...and cooling degree-days (CDD) for the historical (1981-2010) and future (2080-2099) periods in the United States using median results from the Climate Model Intercomparison Project phase 5 (CMIP5) simulations under the Representation Concentration Pathway 8.5 (RCP8.5) scenario. We project future HDD and CDD values by adding CMIP5 projected changes to values based on historical observations of US climate. The sum HDD + CDD is an indicator of locations that are thermally comfortable, with low heating and cooling demand. By the end of the century, station median HDD + CDD will be reduced in the contiguous US, decreasing in the North and increasing in the South. Under the unmitigated RCP8.5 scenario, by the end of this century, in terms of HDD and CDD values considered separately, future New York, NY, is anticipated to become more like present Oklahoma City, OK; Denver, CO, becomes more like Raleigh, NC, and Seattle, WA, becomes more like San Jose, CA. These results serve as an indicator of projected climate change and can help inform decision-making.
Net anthropogenic emissions of carbon dioxide (CO
) must approach zero by mid-century (2050) in order to stabilize the global mean temperature at the level targeted by international efforts
. Yet ...continued expansion of fossil-fuel-burning energy infrastructure implies already 'committed' future CO
emissions
. Here we use detailed datasets of existing fossil-fuel energy infrastructure in 2018 to estimate regional and sectoral patterns of committed CO
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
(with a range of 226 to 1,479 gigatonnes CO
, 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
. Committed emissions from existing and proposed energy infrastructure (about 846 gigatonnes CO
) 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
)
, 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
)
. The remaining carbon budget estimates are varied and nuanced
, and depend on the climate target and the availability of large-scale negative emissions
. Nevertheless, our estimates suggest that little or no new CO
-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
. 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
.
The distribution of anthropogenic aerosols' climate effects depends on the geographic distribution of the aerosols themselves. Yet many scientific and policy discussions ignore the role of emission ...location when evaluating aerosols' climate impacts. Here, we present new climate model results demonstrating divergent climate responses to a fixed amount and composition of aerosol-emulating China's present-day emissions-emitted from 8 key geopolitical regions. The aerosols' global-mean cooling effect is fourteen times greater when emitted from the highest impact emitting region (Western Europe) than from the lowest (India). Further, radiative forcing, a widely used climate response proxy, fails as an effective predictor of global-mean cooling for national-scale aerosol emissions in our simulations; global-mean forcing-to-cooling efficacy differs fivefold depending on emitting region. This suggests that climate accounting should differentiate between aerosols emitted from different countries and that aerosol emissions' evolving geographic distribution will impact the global-scale magnitude and spatial distribution of climate change.
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 CO2 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 years. We evaluate uncertainties in timing and amount of warming, partitioning them into three contributing factors: carbon cycle, climate sensitivity and ocean thermal inertia. If uncertainty in any one factor is reduced to zero without reducing uncertainty in the other factors, the majority of overall uncertainty remains. Thus, narrowing uncertainty in century-scale warming depends on narrowing uncertainty in all contributing factors. Our results indicate that benefit from avoided climate damage from avoided CO2 emissions will be manifested within the lifetimes of people who acted to avoid that emission. While such avoidance could be expected to benefit future generations, there is potential for emissions avoidance to provide substantial benefit to current generations.
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 institute policy changes that discourage inflation of author lists and that encourage the funding of research conducted by single investigators and small groups of researchers.
Arctic amplification is a consequence of surface albedo, cloud, and temperature feedbacks, as well as poleward oceanic and atmospheric heat transport. However, the relative impact of changes in sea ...surface temperature (SST) patterns and ocean heat flux sourced from different regions on Arctic temperatures are not well constrained. We modify ocean-to-atmosphere heat fluxes in the North Pacific and North Atlantic in a climate model to determine the sensitivity of Arctic temperatures to zonal heterogeneities in northern hemisphere SST patterns. Both positive and negative ocean heat flux perturbations from the North Pacific result in greater global and Arctic surface air temperature anomalies than equivalent magnitude perturbations from the North Atlantic; a response we primarily attribute to greater moisture flux from the subpolar extratropics to Arctic. Enhanced poleward latent heat and moisture transport drive sea-ice retreat and low-cloud formation in the Arctic, amplifying Arctic surface warming through the ice-albedo feedback and infrared warming effect of low clouds. Our results imply that global climate sensitivity may be dependent on patterns of ocean heat flux in the northern hemisphere.
supply chain of CO2 emissions Davis, Steven J; Peters, Glen P; Caldeira, Ken
Proceedings of the National Academy of Sciences - PNAS,
11/2011, Letnik:
108, Številka:
45
Journal Article
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CO2 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 chain of global CO2 emissions, finding that 10.2 billion tons CO2 or 37% of global emissions are from fossil fuels traded internationally and an additional 6.4 billion tons CO2 or 23% of global emissions are embodied in traded goods. Our results reveal vulnerabilities and benefits related to current patterns of energy use that are relevant to climate and energy policy. In particular, if a consistent and unavoidable price were imposed on CO2 emissions somewhere along the supply chain, then all of the parties along the supply chain would seek to impose that price to generate revenue from taxes collected or permits sold. The geographical concentration of carbon-based fuels and relatively small number of parties involved in extracting and refining those fuels suggest that regulation at the wellhead, mine mouth, or refinery might minimize transaction costs as well as opportunities for leakage.
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