Aerosol pollution impacts on climate projections
Lead Research Organisation:
University of Leeds
Department Name: School of Earth and Environment
Abstract
The Met Office is tasked with providing up to date information on how climate change will impact the UK. A key part of this task is understanding and exploring current uncertainties in climate processes and what they imply for projected future climate. This PhD project will explore and quantify the effect of large uncertainties related to how aerosol pollution affects climate.
The Intergovernmental Panel on Climate Change estimates that changes in aerosols over the industrial period have caused a radiative forcing of between -0.1 to -2 W/m2. This large cooling effect is comparable in magnitude to the warming effect of greenhouse gases, so aerosol pollution is a major driver of climate change. The uncertainty surrounding aerosols influences future climate projections in two ways. First, it influences how well we understand simulated historical climate, which directly affects our confidence in future projections. Second, there are likely to be rapid reductions in aerosol pollution over the next 2-4 decades, which will strongly influence how the warming will accelerate.
The project will use large ensembles of model simulations combined with extensive observational data from ground sites, ships, aircraft and satellites to narrow the uncertainty in model simulations and climate projections.
This is a collaborative project with the Met Office "Understanding Climate Change" department, co-supervised by Dr Ben Booth. The project would suit students who are interested in pursuing a career in climate sciences, as well as maths and computing students who want to apply their skills to challenging new problems.
The main research question are:
1) What are the main causes of uncertainty in aerosol effects on regional and global climate?
2) How much can the uncertainty realistically be reduced by constraining aerosol and cloud model processes using observations?
3) What effect does narrowing the range of aerosol forcing considered plausible imply for future projections? Are some of the projected changes more plausible than others?
The research is related to the next update of the UK Climate Projections in 2018 (UK18). The Met Office will release climate data that will inform the UK's 3rd national Climate Change Risk Assessment. The project will provide a wider context on the plausibility of the range of aerosol processes in the UK18 projections, and identify model-observed comparisons that can be used in updates to projections beyond 2018.
The Intergovernmental Panel on Climate Change estimates that changes in aerosols over the industrial period have caused a radiative forcing of between -0.1 to -2 W/m2. This large cooling effect is comparable in magnitude to the warming effect of greenhouse gases, so aerosol pollution is a major driver of climate change. The uncertainty surrounding aerosols influences future climate projections in two ways. First, it influences how well we understand simulated historical climate, which directly affects our confidence in future projections. Second, there are likely to be rapid reductions in aerosol pollution over the next 2-4 decades, which will strongly influence how the warming will accelerate.
The project will use large ensembles of model simulations combined with extensive observational data from ground sites, ships, aircraft and satellites to narrow the uncertainty in model simulations and climate projections.
This is a collaborative project with the Met Office "Understanding Climate Change" department, co-supervised by Dr Ben Booth. The project would suit students who are interested in pursuing a career in climate sciences, as well as maths and computing students who want to apply their skills to challenging new problems.
The main research question are:
1) What are the main causes of uncertainty in aerosol effects on regional and global climate?
2) How much can the uncertainty realistically be reduced by constraining aerosol and cloud model processes using observations?
3) What effect does narrowing the range of aerosol forcing considered plausible imply for future projections? Are some of the projected changes more plausible than others?
The research is related to the next update of the UK Climate Projections in 2018 (UK18). The Met Office will release climate data that will inform the UK's 3rd national Climate Change Risk Assessment. The project will provide a wider context on the plausibility of the range of aerosol processes in the UK18 projections, and identify model-observed comparisons that can be used in updates to projections beyond 2018.
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| NE/P010547/1 | 01/10/2017 | 31/03/2022 | |||
| 1935152 | Studentship | NE/P010547/1 | 01/10/2017 | 31/03/2022 |
| Description | Atmospheric aerosols have caused a net cooling of climate over the industrial period that has offset some of the warming of greenhouse gases. Globally aerosol emissions are predicted to decline in the coming decades in line with air quality and climate change mitigation policies. Reductions in aerosols will cause a near-term warming of climate and corresponding aerosol-driven climate responses. Hence, it is important we can accurately predict the impact of aerosols on climate. However, the interactions of aerosols with clouds and solar radiation remains one of the most uncertain aspects of climate modelling. In this project we have used an ensemble of climate model simulations alongside statistical techniques to first quantify the impact of uncertainty in the radiative effect of aerosols in near-term climate projections, and show this uncertainty can alter the projected year for exceedance of the 1.5? target set by the Paris Agreement by 4 years. Secondly, we have further investigated how the uncertainty in aerosol radiative can impact large-scale dynamical climate changes, such as shifts in tropical rainfall, based on our understanding of historical climate changes. We find accounting for single-model uncertainty and a greater influence from internal variability can obscure a relationship between anthropogenic aerosol forcing and tropical precipitation shifts over the 20th century. Yet, there is a clear influence of major volcanic eruptions on precipitation shifts. However, in the future, under a high greenhouse gas emission scenario, there is relationship between the magnitude of aerosol forcing and tropical precipitation shifts up to mid-21st century. This result, further illustrates how the uncertainty in aerosol radiative forcing limits the accuracy of future climate projections. Lastly, we have explored the use of trends in surface solar radiation over Europe as a measure of climate model performance and as a constraint on aeosol radaitive forcing. Our results suggest caution is needed when using surface solar radiation as a model constraint because model performance, model parameter influence and the relationship with aerosol radiative forcing varies between time periods when anthropogenic aerosol emissions increased compared to periods when emissions decreased, seasons, the degree of ocean coupling in the model, and the model ensemble size. |
| Exploitation Route | Current emission reduction commitments suggest a global mean temperature rise of 1.5? since pre-industrial times will likely happen during the next two decades. This gives little time to put in place adaptation measures that limit the impact of the increased climate change. Our first paper has shown that when taking into account the parametric uncertainty in aerosol radiative forcing the timing of reaching 1.5? for for a middle of the road scenario is between 2034 and 2039. Our second paper shows that the magnitude of aerosol radiative forcing has a strong relationship with the strength in projected tropical precipitation shifts up to mid-21st century. The impact of aerosol radiative forcing uncertainty on temperature and precipitation projections illustrates the need for the continued effort in reducing aerosol radiative forcing uncertainty, in order for successful implementation of climate change mitigation and adaptation policies. |
| Sectors | Environment |