Earth Systems

Mercury Benefits of Climate Policy in China: Addressing the Paris Agreement and the Minamata Convention Simultaneously

Absract: National commitments under the Paris Agreement on climate change interact with other global environmental objectives, such as those of the Minamata Convention on Mercury. We assess how mercury emissions and deposition reductions from national climate policy in China under the Paris Agreement could contribute to the country's commitments under the Minamata Convention. We examine emissions under climate policy scenarios developed using a computable general equilibrium model of China's economy, end-of-pipe control scenarios that meet China's commitments under the Minamata Convention, and these policies in combination, and evaluate deposition using a global atmospheric transport model. We find climate policy in China can provide mercury benefits when implemented with Minamata policy, achieving in the year 2030 approximately 5% additional reduction in mercury emissions and deposition in China when climate policy achieves a 5% reduction per year in carbon intensity (CO2 emissions 9.7 Gt in 2030). This corresponds to 63 Mg additional mercury emissions reductions in 2030 when implemented with Minamata Convention policy, compared to Minamata policy implemented alone. Climate policy provides emissions reductions in sectors not considered under the Minamata Convention, such as residential combustion. This changes the combination of sectors that contribute to emissions reductions.

Can a growing world be fed when the climate is changing?

Abstract: We study the capacity to meet food demand under conditions of climate change, economic and population growth. We take a novel approach to quantifying climate impacts, based on a model of the global economy structurally estimated on the period 1960 to 2015. The model integrates several features necessary to study the problem, including an explicit agriculture sector, endogenous fertility, directed technical change and fossil/renewable energy. We estimate the world economy is more than one trillion dollars smaller, and world population more than 80 million smaller, than would have been the case without climate change. This is despite substantial adaptation having taken place in general equilibrium through R&D and agricultural land expansion. Policy experiments with the model suggest that optimal GHG taxes are high and future temperatures held well below 2°C.

On December 3 and 4, Boston University convened a workshop exploring how synthetic biology—the engineering of genetic “circuits” in living cells and organisms to enable them to perform specified tasks—can help address climate change. Participants, who included thought leaders in science, economics, policy and ethics, considered a wide range of complex challenges and potential benefits of proposed synthetic biology approaches to reducing greenhouse gas emissions.

Synthetic biology: A new tool to tackle climate change?
Underestimating Internal Variability Leads to Narrow Estimates of Climate System Properties

Abstract: Probabilistic estimates of climate system properties often rely on the comparison of model simulations to observed temperature records and an estimate of the internal climate variability. In this study, we investigate the sensitivity of probability distributions for climate system properties in the Massachusetts Institute of Technology Earth System Model to the internal variability estimate. In particular, we derive probability distributions using the internal variability extracted from 25 different Coupled Model Intercomparison Project Phase 5 models. We further test the sensitivity by pooling variability estimates from models with similar characteristics. We find the distributions to be highly sensitive when estimating the internal variability from a single model. When merging the variability estimates across multiple models, the distributions tend to converge to a wider distribution for all properties. This suggests that using a single model to approximate the internal climate variability produces distributions that are too narrow and do not fully represent the uncertainty in the climate system property estimates.

Statistical emulators of irrigated crop yields and irrigation water requirements

Summary: In a previous paper focused on four major rain-fed breadbasket crops—maize, rice, soybean and wheat—the author developed a set of crop yield statistical emulators and showed that they could produce results comparable to those generated by an ensemble of global gridded crop model (GGCM) simulations upon which they were trained. This new study provides statistical emulators of GGCMs to estimate irrigated crop yields and associated irrigation water withdrawals for maize, rice, soybean and wheat. Those emulators are estimated using data from an ensemble of simulations from five GGCMs from the Inter-Sectoral Impact Model Intercomparison Project Fast Track project. Crop-specific response functions for each GGCM are estimated at the grid-cell level over the globe. Validation exercises confirm that the statistical emulators are able to replicate the crop models’ spatial patterns of irrigated crop yields and irrigation water withdrawals reasonably well, both in terms of levels and changes over time, although accuracy varies by model and by region. This study therefore provides a reliable and computationally efficient alternative to global gridded crop models.

 

 

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