Publications

Export 7 results:
Sort by: Author Title Type [ Year  (Desc)]
2019
Lelieveld, J, Klingmuller K, Pozzer A, Burnett RT, Haines A, Ramanathan V.  2019.  Effects of fossil fuel and total anthropogenic emission removal on public health and climate. Proceedings of the National Academy of Sciences of the United States of America. 116:7192-7197.   10.1073/pnas.1819989116   AbstractWebsite

Anthropogenic greenhouse gases and aerosols are associated with climate change and human health risks. We used a global model to estimate the climate and public health outcomes attributable to fossil fuel use, indicating the potential benefits of a phaseout. We show that it can avoid an excess mortality rate of 3.61 (2.96-4.21) million per year from outdoor air pollution worldwide. This could be up to 5.55 (4.52-6.52) million per year by additionally controlling nonfossil anthropogenic sources. Globally, fossil-fuel-related emissions account for about 65% of the excess mortality, and 70% of the climate cooling by anthropogenic aerosols. The chemical influence of air pollution on aeolian dust contributes to the aerosol cooling. Because aerosols affect the hydrologic cycle, removing the anthropogenic emissions in the model increases rainfall by 10-70% over densely populated regions in India and 10-30% over northern China, and by 10-40% over Central America, West Africa, and the droughtprone Sahel, thus contributing to water and food security. Since aerosols mask the anthropogenic rise in global temperature, removing fossil-fuel-generated particles liberates 0.51(+/- 0.03) degrees C and all pollution particles 0.73(+/- 0.03) degrees C warming, reaching around 2 degrees C over North America and Northeast Asia. The steep temperature increase from removing aerosols can be moderated to about 0.36(+/- 0.06) degrees C globally by the simultaneous reduction of tropospheric ozone and methane. We conclude that a rapid phaseout of fossil-fuel-related emissions and major reductions of other anthropogenic sources are needed to save millions of lives, restore aerosol-perturbed rainfall patterns, and limit global warming to 2 degrees C.

2017
Xu, YY, Ramanathan V.  2017.  Well below 2 degrees C: Mitigation strategies for avoiding dangerous to catastrophic climate changes. Proceedings of the National Academy of Sciences of the United States of America. 114:10315-10323.   10.1073/pnas.1618481114   AbstractWebsite

The historic Paris Agreement calls for limiting global temperature rise to "well below 2 degrees C." Because of uncertainties in emission scenarios, climate, and carbon cycle feedback, we interpret the Paris Agreement in terms of three climate risk categories and bring in considerations of low-probability (5%) high-impact (LPHI) warming in addition to the central (similar to 50% probability) value. The current risk category of dangerous warming is extended to more categories, which are defined by us here as follows: >1.5 degrees C as dangerous; >3 degrees C as catastrophic; and >5 degrees C as unknown, implying beyond catastrophic, including existential threats. With unchecked emissions, the central warming can reach the dangerous level within three decades, with the LPHI warming becoming catastrophic by 2050. We outline a three-lever strategy to limit the central warming below the dangerous level and the LPHI below the catastrophic level, both in the near term (<2050) and in the long term (2100): the carbon neutral (CN) lever to achieve zero net emissions of CO2, the super pollutant (SP) lever to mitigate short-lived climate pollutants, and the carbon extraction and sequestration (CES) lever to thin the atmospheric CO2 blanket. Pulling on both CN and SP levers and bending the emissions curve by 2020 can keep the central warming below dangerous levels. To limit the LPHI warming below dangerous levels, the CES lever must be pulled as well to extract as much as 1 trillion tons of CO2 before 2100 to both limit the preindustrial to 2100 cumulative net CO2 emissions to 2.2 trillion tons and bend the warming curve to a cooling trend.

2015
Jeuland, MA, Bhojvaid V, Kar A, Lewis JJ, Patange O, Pattanayak SK, Ramanathan N, Rehman IH, Soo JST, Ramanathan V.  2015.  Preferences for improved cook stoves: Evidence from rural villages in north India. Energy Economics. 52:287-298.   10.1016/j.eneco.2015.11.010   AbstractWebsite

Because emissions from solid fuel burning in traditional stoves impact global climate change, the regional environment, and household health, there is today real interest in improved cook stoves (ICS). Nonetheless, surprisingly little is known about what households like about these energy products. We report on preferences for biomass-burning ICS attributes in a large sample of 2120 rural households in north India, a global hotspot for biomass fuel use and the damages that such use entails. Households have a strong baseline reliance and preference for traditional stoves, a preference that outweighs the $10 and $5 willingness to pay (WTP) for realistic (33%) reductions in smoke emissions and fuel needs on average, respectively. Preferences for stove attributes are also highly varied, and correlated with a number of household characteristics (e.g. expenditures, gender of household head, patience and risk preferences). These results suggest that households exhibit cautious interest in some aspects of ICS, but that widespread adoption is unlikely because many households appear to prefer traditional stoves over ICS with similar characteristics. The policy community must therefore support a reinvigorated supply chain with complementary infrastructure investments, foster experimentation with products, encourage continued applied research and knowledge generation, and provide appropriate incentives to consumers, if ICS distribution is to be scaled up. (C) 2015 Elsevier B.V. All rights reserved.

2014
Bhojvaid, V, Jeuland M, Kar A, Lewis JJ, Pattanayak SK, Ramanathan N, Ramanathan V, Rehman IH.  2014.  How do people in rural India perceive improved stoves and clean fuel? Evidence from Uttar Pradesh and Uttarakhand International Journal of Environmental Research and Public Health. 11:1341-1358.   10.3390/ijerph110201341   AbstractWebsite

Improved cook stoves (ICS) have been widely touted for their potential to deliver the triple benefits of improved household health and time savings, reduced deforestation and local environmental degradation, and reduced emissions of black carbon, a significant short-term contributor to global climate change. Yet diffusion of ICS technologies among potential users in many low-income settings, including India, remains slow, despite decades of promotion. This paper explores the variation in perceptions of and preferences for ICS in Uttar Pradesh and Uttarakhand, as revealed through a series of semi-structured focus groups and interviews from 11 rural villages or hamlets. We find cautious interest in new ICS technologies, and observe that preferences for ICS are positively related to perceptions of health and time savings. Other respondent and community characteristics, e. g., gender, education, prior experience with clean stoves and institutions promoting similar technologies, and social norms as perceived through the actions of neighbours, also appear important. Though they cannot be considered representative, our results suggest that efforts to increase adoption and use of ICS in rural India will likely require a combination of supply-chain improvements and carefully designed social marketing and promotion campaigns, and possibly incentives, to reduce the up-front cost of stoves.

2010
Ramanathan, V, Xu YY.  2010.  The Copenhagen Accord for limiting global warming: Criteria, constraints, and available avenues. Proceedings of the National Academy of Sciences of the United States of America. 107:8055-8062.   10.1073/pnas.1002293107   AbstractWebsite

At last, all the major emitters of greenhouse gases (GHGs) have agreed under the Copenhagen Accord that global average temperature increase should be kept below 2 degrees C. This study develops the criteria for limiting the warming below 2 degrees C, identifies the constraints imposed on policy makers, and explores available mitigation avenues. One important criterion is that the radiant energy added by human activities should not exceed 2.5 (range: 1.7-4) watts per square meter (Wm(-2)) of the Earth's surface. The blanket of man-made GHGs has already added 3 (range: 2.6-3.5) Wm(-2). Even if GHG emissions peak in 2015, the radiant energy barrier will be exceeded by 100%, requiring simultaneous pursuit of three avenues: (i) reduce the rate of thickening of the blanket by stabilizing CO(2) concentration below 441 ppm during this century (a massive decarbonization of the energy sector is necessary to accomplish this Herculean task), (ii) ensure that air pollution laws that reduce the masking effect of cooling aerosols be made radiant energy-neutral by reductions in black carbon and ozone, and (iii) thin the blanket by reducing emissions of short-lived GHGs. Methane and hydrofluorocarbons emerge as the prime targets. These actions, even if we are restricted to available technologies for avenues ii and iii, can reduce the probability of exceeding the 2 degrees C barrier before 2050 to less than 10%, and before 2100 to less than 50%. With such actions, the four decades we have until 2050 should be exploited to develop and scale-up revolutionary technologies to restrict the warming to less than 1.5 degrees C.

2009
Ramanathan, V, Feng Y.  2009.  Air pollution, greenhouse gases and climate change: Global and regional perspectives. Atmospheric Environment. 43:37-50.   10.1016/j.atmosenv.2008.09.063   AbstractWebsite

Greenhouse gases (GHGs) warm the Surface and the atmosphere with significant implications for rainfall, retreat of glaciers and sea ice, sea level, among other factors. About 30 years ago, it was recognized that the increase in tropospheric ozone from air pollution (NO(x), CO and others) is an important greenhouse forcing term. In addition, the recognition of chlorofluorocarbons (CFCs) on stratospheric ozone and its climate effects linked chemistry and climate strongly. What is less recognized, however, is a comparably major global problem dealing with air pollution. Until about ten years ago, air pollution was thought to be just an urban or a local problem. But new data have revealed that air pollution is transported across continents and ocean basins due to fast long-range transport, resulting in trans-oceanic and trans-continental plumes of atmospheric brown Clouds (ABCs) containing sub micron size particles, i.e., aerosols. ABCs intercept Sunlight by absorbing as well as reflecting it, both of which lead to a large surface dimming. The dimming effect is enhanced further because aerosols may nucleate more cloud droplets, which makes the clouds reflect More solar radiation. The dimming has a Surface cooling effect and decreases evaporation of moisture from the surface, thus slows down the hydrological cycle. On the other hand, absorption of solar radiation by black carbon and some organics increase atmospheric hearing and tend to amplify greenhouse warming of the atmosphere. ABCs are concentrated in regional and mega-city hot spots. Long-range transport from these hot spots causes widespread plumes over the adjacent oceans. Such a pattern Of regionally concentrated Surface dimming and atmospheric Solar heating, accompanied by widespread dimming over the oceans, gives rise to large regional effects. Only during the last decade, we have begun to comprehend the surprisingly large regional impacts. In S. Asia and N. Africa, the large north-south gradient in the ABC dimming has altered both the north-south gradients in sea Surface temperatures and land-ocean contrast in surface temperatures, which in turn slow down the monsoon circulation and decrease rainfall over the continents. On the other hand, heating by black carbon warms the atmosphere at elevated levels from 2 to 6 kin, where most tropical glaciers are located, thus strengthening the effect of GHGs on retreat of snow packs and glaciers in the Hindu Kush-Himalaya-Tibetan glaciers. Globally, the surface cooling effect of ABCs may have masked as Much 47% of the global warming by greenhouse gases, with an uncertainty range of 20-80%. This presents a dilemma since efforts to curb air pollution may unmask the ABC cooling effect and enhance the surface warming. Thus efforts to reduce GHGs and air pollution should be done under one common framework. The uncertainties in our understanding of the ABC effects are large, but we are discovering new ways in which human activities are changing the climate and the environment. (C) 2008 Elsevier Ltd. All rights reserved.

2006
Auffhammer, M, Ramanathan V, Vincent JR.  2006.  Integrated model shows that atmospheric brown clouds and greenhouse gases have reduced rice harvests in India. Proceedings of the National Academy of Sciences of the United States of America. 103:19668-19672.   10.1073/pnas.0609584104   AbstractWebsite

Previous studies have found that atmospheric brown clouds partially offset the warming effects of greenhouse gases. This finding suggests a tradeoff between the impacts of reducing emissions of aerosols and greenhouse gases. Results from a statistical model of historical rice harvests in India, coupled with regional climate scenarios from a parallel climate model, indicate that joint reductions in brown clouds and greenhouse gases would in fact have complementary, positive impacts on harvests. The results also imply that adverse climate changes due to brown clouds and greenhouse gases contributed to the slowdown in harvest growth that occurred during the past two decades.