Let it snow
A top-down approach to projecting market impacts of climate change
Derek Lemoine & Sarah Kapnick
Nature Climate Change, January 2016, Pages 51–55
Abstract:
To evaluate policies to reduce greenhouse-gas emissions, economic models require estimates of how future climate change will affect well-being. So far, nearly all estimates of the economic impacts of future warming have been developed by combining estimates of impacts in individual sectors of the economy. Recent work has used variation in warming over time and space to produce top-down estimates of how past climate and weather shocks have affected economic output. Here we propose a statistical framework for converting these top-down estimates of past economic costs of regional warming into projections of the economic cost of future global warming. Combining the latest physical climate models, socioeconomic projections, and economic estimates of past impacts, we find that future warming could raise the expected rate of economic growth in richer countries, reduce the expected rate of economic growth in poorer countries, and increase the variability of growth by increasing the climate’s variability. This study suggests we should rethink the focus on global impacts and the use of deterministic frameworks for modelling impacts and policy.
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How Has Human-Induced Climate Change Affected California Drought Risk?
Linyin Cheng et al.
Journal of Climate, January 2016, Pages 111–120
Abstract:
The current California drought has cast a heavy burden on statewide agriculture and water resources, further exacerbated by concurrent extreme high temperatures. Furthermore, industrial-era global radiative forcing brings into question the role of long-term climate change with regard to California drought. How has human-induced climate change affected California drought risk? Here, observations and model experimentation are applied to characterize this drought employing metrics that synthesize drought duration, cumulative precipitation deficit, and soil moisture depletion. The model simulations show that increases in radiative forcing since the late nineteenth century induce both increased annual precipitation and increased surface temperature over California, consistent with prior model studies and with observed long-term change. As a result, there is no material difference in the frequency of droughts defined using bivariate indicators of precipitation and near-surface (10 cm) soil moisture, because shallow soil moisture responds most sensitively to increased evaporation driven by warming, which compensates the increase in the precipitation. However, when using soil moisture within a deep root zone layer (1 m) as covariate, droughts become less frequent because deep soil moisture responds most sensitively to increased precipitation. The results illustrate the different land surface responses to anthropogenic forcing that are relevant for near-surface moisture exchange and for root zone moisture availability. The latter is especially relevant for agricultural impacts as the deep layer dictates moisture availability for plants, trees, and many crops. The results thus indicate that the net effect of climate change has made agricultural drought less likely and that the current severe impacts of drought on California’s agriculture have not been substantially caused by long-term climate changes.
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Did the Kyoto Protocol fail? An evaluation of the effect of the Kyoto Protocol on CO2 emissions
Nicole Grunewald & Inmaculada Martinez-Zarzoso
Environment and Development Economics, February 2016, Pages 1-22
Abstract:
In this paper, we empirically investigate the impact of the Kyoto Protocol on CO2 emissions using a sample of 170 countries over the period 1992–2009. We propose the use of a difference-in-differences estimator with matching to address the endogeneity of the policy variable, namely Kyoto commitments. Countries are matched according to observable characteristics to create a suitable counterfactual. We correspondingly estimate a panel data model for the whole sample and the matched sample and compare the results to those obtained using an instrumental variable approach. The main results indicate that Kyoto Protocol commitments have a measurable reducing effect on CO2 emissions, indicating that a treaty often deemed a ‘failure’ may in fact be producing some non-negligible effects for those who signed it.
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Carbon emissions in China: How far can new efforts bend the curve?
Xiliang Zhang et al.
Energy Economics, forthcoming
Abstract:
While China is on track to meet its global climate commitments through 2020, China’s post-2020 CO2 emissions trajectory is highly uncertain, with projections varying widely across studies. Over the past year, the Chinese government has announced new policy directives to deepen economic reform, protect the environment, and limit fossil energy use in China. To evaluate how new policy directives could affect energy and climate change outcomes, we simulate two levels of policy effort — a Continued Effort scenario that extends current policies beyond 2020 and an Accelerated Effort scenario that reflects newly announced policies — on the evolution of China’s energy and economic system over the next several decades. We perform simulations using the China-in-Global Energy Model, C-GEM, a bespoke recursive-dynamic computable general equilibrium model with global coverage and detailed calibration of China’s economy and future trends. Importantly, we find that both levels of policy effort would bend down the CO2 emissions trajectory before 2050 without undermining economic development. Specifically, in the Accelerated Effort scenario, we find that coal use peaks around 2020, and CO2 emissions level off around 2030 at 10 bmt, without undermining continued economic growth consistent with China reaching the status of a “well-off society” by 2050.
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Climate change, rice crops, and violence: Evidence from Indonesia
Raul Caruso, Ilaria Petrarca & Roberto Ricciuti
Journal of Peace Research, January 2016, Pages 66-83
Abstract:
This article contributes to the literature on the nexus between climate change and violence by focusing on Indonesia over the period 1993–2003. Rice is the staple food in Indonesia and we investigate whether its scarcity can be blamed for fueling violence. Following insights from the natural science literature, which claims that increases in minimum temperature reduce rice yields, we maintain that increases in minimum temperature reduce food availability in many provinces, which in turn raises the emergence of actual violence. We adopt an instrumental variable approach and select the instruments taking into account the rice growing calendar. Results show that an increase of the minimum temperature during the core month of the rice growing season, that is, December, determines an increase in violence stimulated by the reduction in future rice production per capita. Results are robust across a number of different functional specifications and estimation methods. From a methodological point of view, we claim that the inconclusive results obtained in this literature may be caused by an overlook of the correct bundle crop/temperature. Studies concentrating on several countries with different crops and using variations of average temperature as a measure of climate change missed the biological mechanism behind the relationship between climate change and violence.
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Michelle Tom, Paul Fischbeck & Chris Hendrickson
Environment Systems and Decisions, forthcoming
Abstract:
This article measures the changes in energy use, blue water footprint, and greenhouse gas (GHG) emissions associated with shifting from current US food consumption patterns to three dietary scenarios, which are based, in part, on the 2010 USDA Dietary Guidelines (US Department of Agriculture and US Department of Health and Human Services in Dietary Guidelines for Americans, 2010, 7th edn, US Government Printing Office, Washington, 2010). Amidst the current overweight and obesity epidemic in the USA, the Dietary Guidelines provide food and beverage recommendations that are intended to help individuals achieve and maintain healthy weight. The three dietary scenarios we examine include (1) reducing Caloric intake levels to achieve “normal” weight without shifting food mix, (2) switching current food mix to USDA recommended food patterns, without reducing Caloric intake, and (3) reducing Caloric intake levels and shifting current food mix to USDA recommended food patterns, which support healthy weight. This study finds that shifting from the current US diet to dietary Scenario 1 decreases energy use, blue water footprint, and GHG emissions by around 9 %, while shifting to dietary Scenario 2 increases energy use by 43 %, blue water footprint by 16 %, and GHG emissions by 11 %. Shifting to dietary Scenario 3, which accounts for both reduced Caloric intake and a shift to the USDA recommended food mix, increases energy use by 38 %, blue water footprint by 10 %, and GHG emissions by 6 %. These perhaps counterintuitive results are primarily due to USDA recommendations for greater Caloric intake of fruits, vegetables, dairy, and fish/seafood, which have relatively high resource use and emissions per Calorie.
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US power plant sites at risk of future sea-level rise
R. Bierkandt, M. Auffhammer & A. Levermann
Environmental Research Letters, December 2015
Abstract:
Unmitigated greenhouse gas emissions may increase global mean sea-level by about 1 meter during this century. Such elevation of the mean sea-level enhances the risk of flooding of coastal areas. We compute the power capacity that is currently out-of-reach of a 100-year coastal flooding but will be exposed to such a flood by the end of the century for different US states, if no adaptation measures are taken. The additional exposed capacity varies strongly among states. For Delaware it is 80% of the mean generated power load. For New York this number is 63% and for Florida 43%. The capacity that needs additional protection compared to today increases by more than 250% for Texas, 90% for Florida and 70% for New York. Current development in power plant building points towards a reduced future exposure to sea-level rise: proposed and planned power plants are less exposed than those which are currently operating. However, power plants that have been retired or canceled were less exposed than those operating at present. If sea-level rise is properly accounted for in future planning, an adaptation to sea-level rise may be costly but possible.
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Enhanced warming of the Northwest Atlantic Ocean under climate change
Vincent Saba et al.
Journal of Geophysical Research: Oceans, forthcoming
Abstract:
The Intergovernmental Panel on Climate Change (IPCC) fifth assessment of projected global and regional ocean temperature change is based on global climate models that have coarse (∼100 km) ocean and atmosphere resolutions. In the Northwest Atlantic, the ensemble of global climate models has a warm bias in sea surface temperature due to a misrepresentation of the Gulf Stream position; thus, existing climate change projections are based on unrealistic regional ocean circulation. Here we compare simulations and an atmospheric CO2 doubling response from four global climate models of varying ocean and atmosphere resolution. We find that the highest resolution climate model (∼10 km ocean, ∼50 km atmosphere) resolves Northwest Atlantic circulation and water mass distribution most accurately. The CO2 doubling response from this model shows that upper-ocean (0–300 m) temperature in the Northwest Atlantic Shelf warms at a rate nearly twice as fast as the coarser models and nearly three times faster than the global average. This enhanced warming is accompanied by an increase in salinity due to a change in water mass distribution that is related to a retreat of the Labrador Current and a northerly shift of the Gulf Stream. Both observations and the climate model demonstrate a robust relationship between a weakening Atlantic Meridional Overturning Circulation (AMOC) and an increase in the proportion of Warm-Temperate Slope Water entering the Northwest Atlantic Shelf. Therefore, prior climate change projections for the Northwest Atlantic may be far too conservative. These results point to the need to improve simulations of basin and regional-scale ocean circulation.
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Ning Lin & Kerry Emanuel
Nature Climate Change, January 2016, Pages 106–111
Abstract:
We define ‘grey swan’ tropical cyclones as high-impact storms that would not be predicted based on history but may be foreseeable using physical knowledge together with historical data. Here we apply a climatological–hydrodynamic method to estimate grey swan tropical cyclone storm surge threat for three highly vulnerable coastal regions. We identify a potentially large risk in the Persian Gulf, where tropical cyclones have never been recorded, and larger-than-expected threats in Cairns, Australia, and Tampa, Florida. Grey swan tropical cyclones striking Tampa, Cairns and Dubai can generate storm surges of about 6 m, 5.7 m and 4 m, respectively, with estimated annual exceedance probabilities of about 1/10,000. With climate change, these probabilities can increase significantly over the twenty-first century (to 1/3,100–1/1,100 in the middle and 1/2,500–1/700 towards the end of the century for Tampa). Worse grey swan tropical cyclones, inducing surges exceeding 11 m in Tampa and 7 m in Dubai, are also revealed with non-negligible probabilities, especially towards the end of the century.
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Household Location Decisions and the Value of Climate Amenities
Paramita Sinha & Maureen Cropper
NBER Working Paper, December 2015
Abstract:
We value climate amenities by estimating a discrete location choice model for U.S. households. The utility of each Metropolitan Statistical Area (MSA) depends on location-specific amenities, earnings opportunities, housing costs, and the cost of moving to the MSA from the household head’s birthplace. We use the estimated trade-off between wages, housing costs and climate amenities to value changes in mean winter and summer temperatures. We find that households sort among MSAs due to heterogeneous tastes for winter and summer temperature. Preferences for winter and summer temperature are negatively correlated: households that prefer milder winters, on average, prefer cooler summers and households that prefer colder winters prefer warmer summers. Households in the Midwest region, on average, have lower marginal willingness to pay to increase winter and reduce summer temperatures than households in the Pacific and South Atlantic census divisions. We use our results to value changes in winter and summer temperature for the period 2020 to 2050 under the B1 (climate-friendly) and A2 (more extreme) climate scenarios. On average, households are willing to pay 1% of income to avoid the B1 scenario and 2.4% of income to avoid the A2 scenario.
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Enhanced weathering strategies for stabilizing climate and averting ocean acidification
Lyla Taylor et al.
Nature Climate Change, forthcoming
Abstract:
Chemical breakdown of rocks, weathering, is an important but very slow part of the carbon cycle that ultimately leads to CO2 being locked up in carbonates on the ocean floor. Artificial acceleration of this carbon sink via distribution of pulverized silicate rocks across terrestrial landscapes may help offset anthropogenic CO2 emissions. We show that idealized enhanced weathering scenarios over less than a third of tropical land could cause significant drawdown of atmospheric CO2 and ameliorate ocean acidification by 2100. Global carbon cycle modelling driven by ensemble Representative Concentration Pathway (RCP) projections of twenty-first-century climate change (RCP8.5, business-as-usual; RCP4.5, medium-level mitigation) indicates that enhanced weathering could lower atmospheric CO2 by 30–300 ppm by 2100, depending mainly on silicate rock application rate (1 kg or 5 kg m−2 yr−1) and composition. At the higher application rate, end-of-century ocean acidification is reversed under RCP4.5 and reduced by about two-thirds under RCP8.5. Additionally, surface ocean aragonite saturation state, a key control on coral calcification rates, is maintained above 3.5 throughout the low latitudes, thereby helping maintain the viability of tropical coral reef ecosystems. However, we highlight major issues of cost, social acceptability, and potential unanticipated consequences that will limit utilization and emphasize the need for urgent efforts to phase down fossil fuel emissions.
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Rapid and highly variable warming of lake surface waters around the globe
Catherine O'Reilly et al.
Geophysical Research Letters, 28 December 2015, Pages 10,773–10,781
Abstract:
In this first worldwide synthesis of in situ and satellite-derived lake data, we find that lake summer surface water temperatures rose rapidly (global mean = 0.34°C decade−1) between 1985 and 2009. Our analyses show that surface water warming rates are dependent on combinations of climate and local characteristics, rather than just lake location, leading to the counterintuitive result that regional consistency in lake warming is the exception, rather than the rule. The most rapidly warming lakes are widely geographically distributed, and their warming is associated with interactions among different climatic factors — from seasonally ice-covered lakes in areas where temperature and solar radiation are increasing while cloud cover is diminishing (0.72°C decade−1) to ice-free lakes experiencing increases in air temperature and solar radiation (0.53°C decade−1). The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes.
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Emre Gençer et al.
Proceedings of the National Academy of Sciences, 29 December 2015, Pages 15821–15826
Abstract:
We introduce a paradigm — “hydricity” — that involves the coproduction of hydrogen and electricity from solar thermal energy and their judicious use to enable a sustainable economy. We identify and implement synergistic integrations while improving each of the two individual processes. When the proposed integrated process is operated in a standalone, solely power production mode, the resulting solar water power cycle can generate electricity with unprecedented efficiencies of 40–46%. Similarly, in standalone hydrogen mode, pressurized hydrogen is produced at efficiencies approaching ∼50%. In the coproduction mode, the coproduced hydrogen is stored for uninterrupted solar power production. When sunlight is unavailable, we envision that the stored hydrogen is used in a “turbine”-based hydrogen water power (H2WP) cycle with the calculated hydrogen-to-electricity efficiency of 65–70%, which is comparable to the fuel cell efficiencies. The H2WP cycle uses much of the same equipment as the solar water power cycle, reducing capital outlays. The overall sun-to-electricity efficiency of the hydricity process, averaged over a 24-h cycle, is shown to approach ∼35%, which is nearly the efficiency attained by using the best multijunction photovoltaic cells along with batteries. In comparison, our proposed process has the following advantages: (i) It stores energy thermochemically with a two- to threefold higher density, (ii) coproduced hydrogen has alternate uses in transportation/chemical/petrochemical industries, and (iii) unlike batteries, the stored energy does not discharge over time and the storage medium does not degrade with repeated uses.
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Recent Southern New York Climate Change: Observations, Mechanisms, and Spatial Context
Gidon Eshel
Journal of Climate, January 2016, Pages 209–226
Abstract:
This paper examines recent southern New York State climate changes as reflected in a detailed hourly climate record collected about 110 km due north of New York City since 1988, including comprehensive surface radiation data. Comparing 1988–2000 and 2001–14 means, the area has warmed, dominated by a 0.5–0.7-K summer warming. Daytime warming exceeds nighttime’s warming. Warming is not due to enhanced downward longwave flux but arises from increased incident solar fluxes accompanying declining aerosol loads. Local warming is shown to stem from a large-scale response to increased solar forcing, the key element of which is an accelerated summer hydrological cycle: increased precipitation, with smaller evaporation increases leading to large, significant soil moisture and runoff increases. Much of the accelerated summer hydrological cycle is shown to arise as a result of an anomalous low-level cyclonic motion centered on the mid-Atlantic U.S. coast, rendering the results regional rather than local. Analyzing the stability and CAPE budgets of mean and individual summer profiles over the studied site provides a diagnostic explanation of the observed warming and accelerated hydrometeorology due to enhanced solar fluxes. The study reveals a complex suite of (thermo)dynamic feedbacks to radiative forcing of which surface warming is but one element, reiterating and re-emphasizing that surface temperature trends may be embedded in far richer physics than greenhouse gas–induced radiative forcing alone.
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Twenty-First-Century Snowfall and Snowpack Changes over the Southern California Mountains
Fengpeng Sun et al.
Journal of Climate, January 2016, Pages 91–110
Abstract:
Future snowfall and snowpack changes over the mountains of Southern California are projected using a new hybrid dynamical–statistical framework. Output from all general circulation models (GCMs) in phase 5 of the Coupled Model Intercomparison Project archive is downscaled to 2-km resolution over the region. Variables pertaining to snow are analyzed for the middle (2041–60) and end (2081–2100) of the twenty-first century under two representative concentration pathway (RCP) scenarios: RCP8.5 (business as usual) and RCP2.6 (mitigation). These four sets of projections are compared with a baseline reconstruction of climate from 1981 to 2000. For both future time slices and scenarios, ensemble-mean total winter snowfall loss is widespread. By the mid-twenty-first century under RCP8.5, ensemble-mean winter snowfall is about 70% of baseline, whereas the corresponding value for RCP2.6 is somewhat higher (about 80% of baseline). By the end of the century, however, the two scenarios diverge significantly. Under RCP8.5, snowfall sees a dramatic further decline; 2081–2100 totals are only about half of baseline totals. Under RCP2.6, only a negligible further reduction from midcentury snowfall totals is seen. Because of the spread in the GCM climate projections, these figures are all associated with large intermodel uncertainty. Snowpack on the ground, as represented by 1 April snow water equivalent is also assessed. Because of enhanced snowmelt, the loss seen in snowpack is generally 50% greater than that seen in winter snowfall. By midcentury under RCP8.5, warming-accelerated spring snowmelt leads to snow-free dates that are about 1–3 weeks earlier than in the baseline period.
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Characterizing the GHG emission impacts of carsharing: A case of Vancouver
Michiko Namazu & Hadi Dowlatabadi
Environmental Research Letters, December 2015
Abstract:
Carsharing exemplifies a growing trend towards service provision displacing ownership of capital goods. We developed a model to quantify the impact of carsharing on greenhouse gas (GHG) emissions. The study took into account different types of households and their trip characteristics. The analysis considers five factors by which carsharing can impact GHG emissions: transportation mode change, fleet vintage, vehicle optimization, more efficient drive trains within each vehicle type, and trip aggregation. Access to carsharing has already been shown to lead some users to relinquish ownership of their personal vehicle. We find that even without a reduction in vehicle-kilometers traveled the change in characteristics of the vehicles used in carsharing fleets can reduce GHGs by more than 30%. Shifting some trips to public transit provides a further 10%–20% reduction in GHGs.