21st Century Sea-Level Rise in Line with the Paris Accord

As global average sea-level rises in the early part of this century there is great interest in how much global and local sea level will change in the forthcoming decades. The Paris Climate Agreement's proposed temperature thresholds of 1.5°C and 2°C have directed the research community to ask what differences occur in the climate system for these two states. We have developed a novel approach to combine climate model outputs that follow specific temperature pathways to make probabilistic projections of sea-level in a 1.5°C and 2°C world. We find median global sea-level (GSL) projections for 1.5°C and 2°C temperature pathways of 44 and 50 cm, respectively. The 90% uncertainty ranges (5%–95%) are both around 48 cm by 2100. In addition, we take an alternative approach to estimate the contribution from ice sheets by using a semi-empirical GSL model. Here we find median projections of 58 and 68 cm for 1.5°C and 2°C temperature pathways. The 90% uncertainty ranges are 67 and 82 cm respectively. Regional projections show similar patterns for both temperature pathways, though differences vary between the median projections (2–10 cm) and 95th percentile (5–20 cm) for the bulk of oceans using process-based approach and 10–15 cm (median) and 15–25 cm (95th percentile) using the semi-empirical approach. Plain Language Summary The sea level you experience at the coast can be estimated by the sum of contributions from ocean expansion, currents, ice melt from glaciers and ice sheets, land-water extraction/damming, and land motion. How sea level changes depends strongly on where you are because each contribution has a unique pattern. We use knowledge of these changes to make projections about future sea-level rise. We estimate how much sea-level could change if societies achieve either of the Paris Climate Agreement's temperature targets by 2100. If we reach 1.5°C or 2.0°C by 2100, GSL should rise around 44–50 cm, respectively. Using a slightly different method we find the global rise could be 58–68 cm. An incomplete picture of the sea-level components means that estimates could be out by up to 80 cm, though all projections show a sea-level rise of at least 20 cm

Stochastic reaction-diffusion kinetics in the microscopic limit

Quantitative analysis of biochemical networks often requires consideration of both spatial and stochastic aspects of chemical processes. Despite significant progress in the field, it is still computationally prohibitive to simulate systems involving many reactants or complex geometries using a microscopic framework that includes the finest length and time scales of diffusion-limited molecular interactions. For this reason, spatially or temporally discretized simulations schemes are commonly used when modeling intracellular reaction networks. The challenge in defining such coarse-grained models is to calculate the correct probabilities of reaction given the microscopic parameters and the uncertainty in the molecular positions introduced by the spatial or temporal discretization. In this paper we have solved this problem for the spatially discretized Reaction-Diffusion Master Equation; this enables a seamless and physically consistent transition from the microscopic to the macroscopic frameworks of reaction-diffusion kinetics. We exemplify the use of the methods by showing that a phosphorylation-dephosphorylation motif, commonly observed in eukaryotic signaling pathways, is predicted to display fluctuations that depend on the geometry of the system

Hydrology: Indo-Gangetic Groundwater Threat

Increasing groundwater extraction supports hundreds of millions of people across the Indo-Gangetic Basin. Data suggests that despite the increase in withdrawals, groundwater depletion is localized and the most widespread threat is contamination