Observations show that the 50-year drying trend (weakening of India summer monsoon) in north central India reversed in the past decade. The finding indicates improved water security and reduced socioeconomic impacts for the region in coming decades.

Background: The Indian summer monsoon (ISM) delivers about 80% of the Indian subcontinent’s annual precipitation and thus impacts the livelihood of more than 1/5 of the world’s population. The timing (typically June – September) and location of the ISM has far-reaching impacts—including floods and droughts—on farming and many other economic activities, and on the availability of water for people and livestock. These factors are of particular concern for north central India, which experienced a significant reduction in summer monsoon rainfall in the second half of the 20th century, resulting in degraded water security and widespread socioeconomic impacts.

Main point: Based on global climate models and multiple hypotheses, scientists expected this drying trend to continue unabated into the 21st century, but a new study in Nature Climate Change shows that the trend has reversed.

Findings: Using data obtained from ground-based and satellite measurements, researchers at the MIT Joint Program on the Science and Policy of Global Change find that since 2002, monsoon rainfall has increased in north central India at a rate of 1.34 millimeters per day per decade. They ascribe the revival of ISM precipitation to a combination of stronger warming over the Indian continent and slower rates of warming over the Indian Ocean. Today’s global climate models—and several hypotheses that have been proposed to explain the long-lasting drying trend in the second half of the 20th century—fail to capture the observed rainfall revival and corresponding trends in the underlying land-ocean temperature differences. In addition, the researchers find that this trend reversal of the Indian summer monsoon  significantly mismatches the overall behavior of Northern Hemispheric monsoonal systems, raising the question of whether conditions unique to India, such as high concentrations of anthropogenic aerosols, are causing this phenomenon.

Significance: Prediction of long-term monsoonal rainfall variations is critical to securing water supplies and planning agricultural and other economic activities in monsoonal regions. Enhanced knowledge about such variations can also help scientists to improve current Earth-system models to more accurately project future climate change.

I investigate the relationship between local government-industry linkages and pollution outcomes in Chinese cities over the period 2003 to 2010. For identification, I rely on the administrative rotation of city mayors, which is determined by political career considerations and retirement age cut-offs but unrelated to their environmental records. These transitions act as plausibly exogenous shocks that disrupt the relationship between the local government and enterprises at the city level. I employ several statistical models to investigate the leadership’s impacts on environmental outcomes.

First, a simple t-test is used to evaluate the change in the pollution index when mayors with particular characteristics enter or leave office. In addition, empirical models are utilized to explore the correlation between mayoral characteristics and changes in city-level pollution. I find correlations between mayoral characteristics and city-level environmental outcomes, focusing specifically on SO₂ emissions, SO₂ emission intensities, and end-of-pipe SO₂ removal ratios. Finally, firm-level data allow me to identify the relationship between mayoral characteristics and pollution by enterprises of specific ownership types.

Mayors with different characteristics show distinct impacts on city-level pollution. I hypothesize that city leaders who have previous experience in industry pay more attention to local economic growth rather than environmental improvements, resulting in increased SO₂ emissions. Consistent with this hypothesis, I find that mayors with industry work background correspond to an increase (decrease) in city-level SO₂ emissions when they enter (leave) office after controlling for city and year fixed effects. Apart from this, I expect that leaders closer to retirement are under less pressure for promotion as they are going to retire soon and due to age cut-offs may not be eligible for higher positions; instead, they may feel less pressure to promote local businesses and pay more attention to environmental management. Evidence shows consistently that tenures of mayors on the verge of retirement are associated with reductions in city-level SO₂ emissions and increases in city-level end-of-pipe SO₂ removal rates.

Further investigation shows that mayors realize their environmental goals via enterprises of specific ownership types. I predict that mayors rotated from the central government are not under pressure of promotion and they are adherent to the central policy in reducing SO₂ emission intensities. I further predict that mayors from the local administration are expected to enforce the usage of SO₂ removal facilities, particularly among enterprises of low level authorities. Consistent with these hypotheses, results show that mayors with work background in central and local governments are associated with improved environmental outcomes, but through different channels. A central government work background results in intensity reduction, but not necessarily SO₂ emissions; however, local government work background is associated with short-term reductions in SO₂ intensities, possibly due to increases in SO₂ removal ratios, particularly among city SOEs.

In addition to the analysis of mayoral characteristics, my research reveals several additional interesting findings. I find that enterprises of lower rank more readily build linkages with local officials not only for economic development but also for environmental management as high-ranking enterprises may face a more stringent monitoring system and are more politically powerful. Implications for environmental policy design in China can be drawn from the results. First, industries are encouraged to behave independently from the government in economic activities as well as policy implementation. Second, environmental performance should be effectively and explicitly included in the evaluation program of officials. Third, government-industry linkages, to the extent that they undermine the economic and policy system, should be minimized as much as possible.