The degree of trust placed in climate model projections is commensurate with how well their uncertainty can be quantified, particularly at timescales relevant to climate policy makers. On inter-annual to decadal timescales, model projection uncertainty due to natural variability dominates at the local level and is imperative to describing near-term and seasonal climate events but difficult to quantify owing to the computational constraints of producing large ensembles.
To this extent, emulators are valuable tools for approximating climate model runs, allowing for the exploration of the uncertainty space surrounding selected climate variables at a substantially reduced computational cost. Most emulators, however, operate at annual to seasonal timescales, leaving out monthly information that may be essential to assessing climate impacts.
This study extends the framework of an existing spatially resolved, annual-scale Earth system model (ESM) emulator (MESMER, Beusch et al., 2020) by a monthly downscaling module (MESMER-M), thus providing local monthly temperatures from local yearly temperatures. We first linearly represent the mean response of the monthly temperature cycle to yearly temperatures using a simple harmonic model, thus maintaining month-to-month correlations and capturing changes in intra-annual variability.
We then construct a month-specific local variability module which generates spatio-temporally correlated residuals with yearly temperature- and month-dependent skewness incorporated within. The emulator's ability to capture the yearly temperature-induced monthly temperature response and its surrounding uncertainty due to natural variability is demonstrated for 38 different ESMs from the sixth phase of the Coupled Model Intercomparison Project (CMIP6). The emulator is furthermore benchmarked using a simple gradient-boosting-regressor-based model trained on biophysical information.
We find that while regional-scale, biophysical feedbacks may induce non-uniformities in the yearly to monthly temperature downscaling relationship, statistical emulation of regional effects shows comparable skill to the more physically informed approach.
Thus, MESMER-M is able to statistically generate ESM-like, large initial-condition ensembles of spatially explicit monthly temperature fields, providing monthly temperature probability distributions which are of critical value to impact assessments.
Coastal loss and damage for small islands
This commentary on a paper in Nature Sustainability reviews how the study quantifies the impacts of sea-level rise on small island states and estimates the impacts in terms of cost, land loss and population exposure across all small islands worldwide.
Risks of synchronised low yields are underestimated in climate and crop model projections
This study finds that the jet stream – air currents in the upper atmosphere – can synchronise extreme weather caused by climate change, resulting in crop failures in multiple countries at the same time.
The deployment length of solar radiation modification: an interplay of mitigation, net-negative emissions and climate uncertainty
Here, we investigate the deployment timescales of solar radiation modification and how they are affected by different levels of mitigation, net-negative emissions and climate uncertainty.
Solar radiation modification: a dangerous distraction from required emissions reductions
Investing precious time and resources in this critical decade to explore SRM technologies distracts from the urgent need to step up mitigation efforts to halve emissions by 2030.
Emissions as usual: implications for the Safeguard Mechanism of LNG and coal mine projects
This report examines the implications of committed and proposed developments in the LNG and coal mining sectors for reform of Australia's Safeguard Mechanism.
Only halving emissions by 2030 can minimise risks of crossing cryosphere thresholds
Institutional decarbonisation scenarios evaluated against the Paris Agreement 1.5°C goal
This study analyses six institutional decarbonisation scenarios published between 2020 and mid 2021 (including four from the oil majors and two from the International Energy Agency. It finds that most of the scenarios would be classified as inconsistent with the Paris Agreement as they fail to limit warming to ‘well below 2 ̊C, let alone 1.5 ̊C, and would exceed the 1.5 ̊C warming limit by a significant margin.
Uncertainty in near-term temperature evolution must not obscure assessments of climate mitigation benefits
This work comments on a study by Samset et al. that found the effects of emission mitigation will only be perceived through global temperature with a multi-decadal delay. This paper provides additional context and expresses concerns with the approach.
An emission pathway classification reflecting the Paris Agreement climate objectives
When categorising pathways in line with the Paris Agreement, the focus has been put on the temperature outcome. Here we propose a pathway based on emission reduction objectives that reflect the climate criteria set out in the Paris Agreement.
No time for complacency: without closing the 2030 gap, net zero targets cannot prevent severe climate impacts
Fossil gas: a bridge to nowhere
This report assesses how fast fossil gas power generation must be phased out in different parts of the world to keep the Paris Agreement’s 1.5°C temperature goal in reach.
Managing climate change risks to world heritage using the In Danger List: Griffith climate action beacon policy discussion paper
This paper considers how the World Heritage Convention’s ‘List of World Heritage in Danger’ could be used more effectively for managing sites threatened by climate change or where climate change has already caused significant degradation.