The ACRG has worked on a number of research projects, is currently involved with four active research projects.
Active Projects:
Constraining the Role of the Marine Sulfur Cycle in the Earth System (CARES)
CARES is a NERC-funded research project aimed at improving our understanding of, constraining, and reducing the current uncertainty in the marine atmospheric sulfur cycle through a combination of ground-breaking field measurements and model simulations.
We will bring together measurements of the broadest range of sulfur compounds to date and will quantify in situ concentrations and fluxes of a large number of exciting, recently discovered sulfur compounds (like HPMTF) as well as cloud and aerosol properties in the Eastern North Atlantic.
A series of Earth system modelling studies, including uncertainty quantification methods, will integrate the knowledge gained from field and laboratory work and enable the global impact of marine sulfur chemistry to be determined under a changing climate.
The main objectives of CARES are:
- Quantify ocean-atmosphere emissions of DMS and CH3SH inside and outside of phytoplankton blooms.
- Quantify the gas phase oxidation rates of DMS and CH3SH and estimate conversions/yields to HPMTF, SO2, MSA and sulfate aerosols.
- Constrain and quantify the loss of SO2 via deposition to the ocean surface and in-cloud oxidation.
- Develop new observationally constrained mechanisms that account for the improved process understanding of marine sulfur chemistry and make these available for use by the wider community of composition climate modellers.
- Quantify the role of the marine sulfur cycle (with the improved understanding) on the climate system and determine metrics such as the effective radiative forcing (ERF) of marine sulfur emissions and the climate system response to these emissions (i.e., the climate feedback parameter).
- Quantify the degree to which the climate effects of marine sulfur emissions are sensitive to atmospheric conditions.
Find out more about CARES on its website.
Hydrogen Emissions: Constraining the Earth System Response (HECTER)
Hydrogen is one of the most abundant gases in our atmosphere but remains poorly understood from a climate perspective. Whilst hydrogen itself does not directly influence the climate, it reacts with the hydroxyl radicals (OH) in the atmosphere, leading to a cascade of chemical feedbacks which influence the abundance of greenhouse gases, as well as ozone in the troposphere and stratosphere.
The HECTER project will improve our understanding of chemical feedbacks from hydrogen by developing an improved process-based representation of the full hydrogen cycle which will be incorporated into new models based on the UK Earth System Model (UKESM). Multi-model analyses will quantify and constrain the uncertainty in the Earth system response to emissions of hydrogen.
The main objectives of HECTER are:
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Constrain the present-day sources and sinks of atmospheric hydrogen.
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Assess impact, including uncertainty, of hydrogen leakage on:
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Hydrogen, methane, ozone, and stratospheric water vapour
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Aerosols and clouds
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Quantify the time evolution of the effects of hydrogen emissions.
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Assess regional variations in radiative forcing from regional perturbations to hydrogen emissions.
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Develop an improved representation of the climate impacts of hydrogen emissions in the FaIR model, for use with new hydrogen emission scenarios created in COSH-AIR.
Discovering reasons for global atmospheric methane growth using deuterium isotopes
The quantity of atmospheric methane is rising rapidly. This growth was unexpected, and presents one of the biggest and most immediate threats to the Paris Agreement. Yet, the reasons behind this growth are largely unknown.
This project, led by the University of London's Department of Earth Sciences and collaborating with numerous other universities in the UK, is focussed on discovering why. Isotopologues can both identify and discriminate between source and sink changes. Therefore, we aim to measure and model deuterium/hydrogen (D/H) isotopes - which can clearly discriminate against methane sources and sinks - to reduce the uncertainties in the global methane budget.
The project plans to use three main measurements:
- Field campaigns to determine isotopic source signatures.
- Time series from remote stations in the North and South hemispheres.
- Modelling to extract global budgets and causes of change.
Once completed, this project will lead to major improvements in our understanding of the global methane budget, and help shape future decisions on the strategies and policies required to stabilise and reduce methane.
A laser spectrometer-based environmental gas and gas-isotope facility (LASER-ENVI)
The LASER-ENVI project brings together many research scientists from across the UK, including the Cambridge's own Department of Earth Sciences.
Earth is only habitable due to its specific composition and pressure of gases. As the concentration of greenhouse gases (GHG) present in our atmosphere is increasing rapidly, tracing the courses, consumption and processes that GHGs are involved in can inform our understanding of planet functioning under stress. In turn, this may help us predict how various process that consume and/or produce GHGs may change under increasing temperatures and rising sea levels.
Measuring the stable isotopic composition of these gases is one of the most powerful tools we have for tracing sources and sinks of gas to the atmosphere. Therefore, as part of LASER-ENVI we aim to measure the isotopic composition of various gases in our atmosphere. This is only possible due to recent technological developments in laser spectroscopy, meaning we are at the forefront of being able to fully resolve the gas cycle across a range of natural environments.
Completed Projects:
Process analysis, observations and modelling - integrated solutions for cleaner air for Delhi (PROMOTE)
Poor air quality and air pollution is a major killer - accounting for approximately 1 in 10 deaths worldwide. PROMOTE is a four-year integrated proposal aimed at reducing uncertainties in air quality prediction and forecasting in Delhi, India that brings together a multi-disciplinary team of researchers from both India and the UK.
As part of PROMOTE we undertake process orientated observational and modelling analysis, to subsequently derive sensitivity relationships to link air pollutant concentrations and emissions control. This knowledge is essential if we are to produce effective mitigation solutions for decreasing the air pollution over Delhi and the surrounding regions.
PROMOTE addresses three key research questions:
- What contribution is made by primary and secondary aerosols to the overall air pollution burden in Delhi during summer and winter conditions?
- How do the interactions between boundary layer dynamics and long-range transport of air pollution contribute to the local air quality of Delhi?
- By taking account of local, urban and regional sources, what are the most effective emission controls for mitigation interventions that will lead to significant reductions in air pollution and exposure levels over Delhi and the wider National Capital Region?
For more information on the PROMOTE project and how we help, check out their website.
The North Atlantic Climate System Integrated Study (ACSIS) 
ACSIS is a five year research programme that brings together a wide range of faculties from within the UK environmental science community.
Changes in the North Atlantic Climate System directly impacts the UK's climate, weather and air quality. Therefore, ACSIS's key goal is the improve the UK's ability to detect, attribute and predict changes in this climate system by integrating historic and novel observations of atmospheric physics, with the chemistry of the ocean state and Arctic sea ice.
By improving our understanding of the North Atlantic Climate System we will be able to predict changes, which can then be exploited to assess the impact of these changes - such as the consequences of hazardous weather risk. ACSIS outputs will also be used to inform policy on climate change adaptation and air quality.
The precise objectives of ACSIS are:
- To provide a quantitative description of how the North Atlantic Climate System is changing across a range of variables.
- To determine the processes that are shaping change in the North Atlantic Climate System now and in the near future.
- To determine the extent to which future changes in the North Atlantic Climate System are predictable.
Find out more information by watching the NCAS video on our Media Links page.
Oxidant Budgets of the Northern Hemisphere (OXBUDS)
The OXBUDS project brought together experts in chemistry climate modelling and organic nitrate chemistry, building upon previous NERC-funded work on the trends of alkanes and and alkyl nitrates in the air.
The hydroxyl radical (OH) is the dominant oxidising agent in the troposphere (the first and lowest layer of Earth's atmosphere). Therefore, the concentration of OH in the atmosphere controls both the abundance and lifetimes of most atmospheric pollutions - including the most important greenhouse gas (GHG), methane.
There are large uncertainties surrounding our current understanding of how these concentrations have changed in the past, and even larger uncertainties surrounding our projections of future changes and their associated climate impacts. OXBUDS aims to use long term trends of alkane and alkyl nitrate concentrations to determine this impact - how changing anthropogenic (human) emissions has affected the ozone and hydroxyl radical (OH) budgets of the northern hemisphere troposphere since 1950.
The mechanisms of oxidation of biogenic hydrocarbons
This project aimed to improve our understanding of the mechanisms behind the oxidation of biogenic hydrocarbons - in particular the oxidation of isoprene.
A mass of isoprene roughly equal to that of the entire human population is emitted into the atmosphere each year. Due to this, and isoprene's high reactivity, it is extremely important to include isoprene chemistry in chemistry-climate models if we are to obtain a full picture of atmospheric processes.
However, the details of isoprene chemistry are known to vary widely between models. So much so that isoprene chemistry has been suggested as a major cause of disagreement between model predictions and secondary pollutants.