Methane emissions from East African wetlands are surging, and this project will pin down exactly how much more will escape as the climate warms. The problem is a dangerous gap in climate models. Current Earth system models cannot accurately represent how changing rainfall, river flows, and wetland vegetation control methane release. This matters because methane is a potent greenhouse gas, and tropical wetlands—especially in Africa—are a major and growing source. Without better predictions, future climate projections remain uncertain. If CurFEW succeeds, the UK Earth System Model will gain improved submodels that realistically simulate how hydrology, vegetation, and methane emissions interact under warming. This will produce more reliable projections of future atmospheric methane levels, feeding directly into national and international climate assessments. African scientists will also gain data to help their countries prepare for emerging environmental challenges. This is primarily fundamental science—improving the process knowledge that underpins climate models. But deeper understanding of these feedbacks could eventually inform water and land management decisions across the tropics, where vast wetland carbon stores are at stake.
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The overall aim of our project is to improve predictions of tropical wetland methane emissions and associated feedbacks in a rapidly-changing climate. We will achieve this by developing and embedding new emission process knowledge, informed by field and laboratory data and by satellite data, into submodels that define the UK Earth System model (UKESM). We focus on Africa for two reasons. First, satellite observations have linked a large fraction of the recent surge in atmospheric methane to wetland emissions from Eastern Africa. Second, Africa exemplifies the compound challenge of accurately describing rainfall, hydrology, vegetation, and the emission of methane, and understanding how they will change in future. To address this challenge, CurFEW necessarily brings together diverse expertise from hydrology, ecology, data assimilation, satellite remote sensing, atmospheric sciences, and wetland dynamics. Previous work by the assembled team has revealed the globally-relevant methane emissions from East African wetlands and documented how they have changed over the past decade. Using satellite observations they have been able to show that a large fraction of observed variations in methane emissions across the tropics is driven by changes in rainfall, driven in turn by large-scale changes in sea surface temperatures (SSTs). Changes in climate driven by rising atmospheric GHGs are expected to cause adjustments to SSTs which led us to propose a new positive climate feedback. Current ESM frameworks are unable to describe these feedbacks because they do not accurately describe the underlying terrestrial processes. In CurFEW, we take a systemic approach to address the key knowledge gaps associated with hydrological dynamics (e.g., increase in runoff, river flow and inundation), and the changes in wetland ecosystems and biogeochemical cycling related to the net release of methane to the atmosphere. These knowledge gaps are relevant to the vast wetland carbon stores across the tropics. Our team comprises world-leading experts that can exploit new satellite, field, and laboratory data to improve how UKESM sub-models of hydrology, vegetation dynamics, and methane emissions will respond to a progressively warmer world. To address our project aim, we have four science questions targeting key uncertainties about how wetland emissions of methane change in a warming world. They necessarily involve integrating models and data on multiple spatial and temporal scales. Q1 What is the role of catchment-scale river hydrodynamics on seasonal and interannual wetland dynamics and on methane emissions? Q2 How strongly does the composition of wetland vegetation (emergent macrophytes such as papyrus and phragmites in perennial wetlands, grasses in seasonal floodplains) control methane emissions? Q3 How will a warming climate impact the future composition, distribution and zonation of wetland vegetation and the associated methane emissions? Q4 At the continental scale, what is the range of future wetland methane emissions under different climate scenarios, and how important are changes in water/land management? CurFEW will deliver a data-driven estimate of future natural methane release from Africa in the presence of climate change and changes in the hydrological cycle. Key research outputs will include: new datasets that lead to insights about the linkages between hydrology, wetland dynamics, vegetation dynamics, and the emissions of methane; improved submodels that define the UKESM; high level peer-review papers; and inputs to national and international assessments. By working with African scientists, we aim to help influence how individual countries address the emerging and contrasting environmental challenges they will face.
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