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Overview

Science+ meeting organised by Professor Jim Hall FREng, Associate Professor Jamie Hannaford and Professor Gabriele Hegerl FRS.

The impacts of droughts on people and the natural environment are increasing, due to climate change and over-exploitation of water resources. This Science+ meeting explored scientific understanding of changing drought risk and examined drought impacts on the environment, people and the economy. Policy-makers, practitioners and scientists discussed policy options for management of droughts in the future.

An accompanying journal issue has been published in Philosophical Transactions of the Royal Society A.

Attending the event

This meeting has taken place. 

Enquiries: contact the Scientific Programmes team

Organisers

Schedule


Chair

Professor Gabriele Hegerl FRS

University of Edinburgh, UK

09:00-09:10
Welcome on behalf of the Royal Society and by Professor Jim Hall FREng

Speakers

Professor Jim Hall FREng

University of Oxford, UK

09:10-09:30
Drought risk in the Anthropocene: from the Jaws of Death to the Waters of Life

Abstract

In his opening address, Sir James Bevan, Chief Executive of the Environment Agency, will set the scene on the Anthropocene: looking at what this new epoch means for humans and nature, how we got here, and where we need to go next. Sir James’ speech will set out the alarming impact that the epoch’s most important feature, climate change caused by human activity, is having on drought risk and extreme weather. In response to these challenges Sir James will look ahead to COP26 and beyond, setting out what needs to be done to mitigate the worst impacts of runaway climate change, and to adapt to impacts that are irrevocable. In particular he will examine what needs to be done to escape what in 2019 he called ‘the Jaws of Death’, the point on water companies’ planning charts some 20 years from now where if we don’t intervene water demand will outstrip supply. He will set out what the Environment Agency is doing alongside business, government, civil society, and what the Royal Society can do to help. Finally he will argue why we should be optimistic we can turn the climate crisis into an opportunity that creates a better place for all.

Speakers

09:30-09:45
Discussion
09:45-10:15
Global drought trends and future projections

Abstract

Drought is one of the most difficult natural hazards to be measured and monitorised, which strongly affects the assessment of recent drought changes and future scenarios. This talk first illustrates some key conceptual issues, which are necessary to be considered when assessing drought changes and related uncertainties; among them it includes the need of considering the different behaviour of different drought types. Secondly, it shows trends in meteorological droughts considering a long-term perspective using precipitation records and also the possible role of global warming processes on trends in drought severity. Finally, the talk shows a review of  studies analysing drought projections for future climate scenarios and it stresses the key concepts and uncertainties that are necessary to consider when assessing drought processes under climate change, including the use of different metrics and modelling approaches. The necessity of establishing differences between the behaviour of the mean climate and the frequency, duration, and spatial extent of droughts, considered as an extreme natural hazard, are emphasised when determining drought changes and future projections. 

Speakers

10:15-10:30
Discussion
10:30-11:00
Coffee break
11:00-11:30
Droughts in a changing climate: Evidence from the IPCC AR6

Abstract

This presentation will provide an overview of the main conclusions of the 6th Assessment report (AR6) from the Intergovernmental Panel on Climate Change (IPCC) on observed and projected changes in droughts. For the first time, a full chapter of the IPCC assessment report (Chapter 11; Seneviratne, Zhang, et al, in press) was dedicated to the topic of weather and climate extremes, including extensive assessments on changes in droughts. The drought assessment was subdivided in changes in meteorological, agricultural and ecological, and hydrological droughts. It was also informed from cross-chapter assessments with AR6 chapters assessing changes in a) the water cycle (Chapter 8), b) climatic impact drivers (Chapter 12), and the c) carbon cycle (Chapter 5), as well as d) the Atlas chapter. Regional assessments were also provided for all considered AR6 regions. Observations reveal that agricultural and ecological droughts have increased in several regions, and that human influence has contributed to increases in some regions due to increases in evapotranspiration. With every increment of global warming, changes in agricultural and ecological droughts become larger in several regions, including West-Central Europe and the Mediterranean region, as well as the Amazon region, among others.

Speakers

11:30-12:00
Did aerosols delay the emergence of greenhouse gas-forced drought in Southwestern North America?

Abstract

Greenhouse gas emissions have likely contributed to current drought conditions in southwestern North America, which is experiencing one of its driest periods on record. But greenhouse gas emissions have risen steadily since the beginning of the Industrial Revolution: why then, have these drought conditions only emerged recently? In fact, in the latter part of the twentieth century regional soil moisture anomalies were unprecedentedly wet. In this talk, Dr Marvel will present a Bayesian method for detection and attribution that quantifies uncertainties, handles multiple external forcings, and can be used for model evaluation. The evidence suggests that aerosol forcing, aided by the eruption of Pinatubo in 1991, partially counteracted greenhouse gas-driven decreases in soil moisture, delaying the emergence of the current anthropogenically forced drought.

Speakers

12:00-12:30
Discussion

Chair

13:30-14:00
Status and Prospects of Drought Forecasting

Abstract

Improving water supply management and decision making in water stressed regions requires reliable seasonal drought prediction, which remains a grand challenge. Over the past decades, a wide range of models, including dynamical, statistical and hybrid dynamical-statistical, have been developed for seasonal precipitation forecasting. However, each type has its own advantages and disadvantages. This presentation offers a review of progress in different types of forecasting methods including numerical/dynamical (eg, North American Multi-Model Ensemble), statistical models (eg, analog-based, ensemble streamflow prediction, artificial intelligence), and hybrid approaches that combine the two. This talk will review different hybrid frameworks such as hierarchical and parallel model concepts. The presentation ends with a discussion on current gaps and opportunities including satellite observations and artificial intelligence techniques. 

Speakers

14:00-14:30
Recent advances in drought monitoring using satellites and models

Speakers

14:30-15:00
Discussion
15:00-15:30
Tea break
15:30-16:00
UK droughts past, present and future: quantifying hydroclimatic variability to inform drought management

Abstract

Water resource managers need to understand hydroclimatic variability to manage droughts. For long-term planning it is essential to understand drought risk, based on past recorded variability and what is likely to happen in future. For managing drought events in the here and now, it is necessary to understand current water availability status, and what is likely to happen over the coming weeks and months. While the UK has a long history of water resources management and well-evolved frameworks for drought planning, at the same time there are inevitable limitations: our understanding of the past is constrained by short observational records, while the utility of future forecasts and projections (whether seasonal or multi-decadal) is inevitably constrained by the uncertainties involved in climate and hydrological modelling. This presentation focuses on recent advances in our understanding of drought variability, largely drawn from the UKRI Drought and Water Scarcity Programme (2014 – 2020). This will include efforts to extend our understanding of past drought variability through hydroclimatic reconstructions, initiatives to provide national-scale, spatially coherent hydrological projections for the 21st century, and the latest advances in status monitoring and seasonal forecasting. Several key themes run through all this work: notably the importance, and challenges, of drought definition and quantification; and the importance of co-development with diverse end-users to ensure the applicability of hydroclimate services in drought management on-the-ground.

Speakers

16:00-16:30
Benchmark worst droughts in India (1901-2020)

Abstract

During the summer monsoon (June-September) season, drought poses challenges for agricultural activities and water availability in India. We develop a framework considering the timing, areal coverage, and severity of droughts that can be used for the assessment as the monsoon season progresses. We estimate the benchmark worst droughts within the monsoon season (June, July, August, and September) using the long-term (1901-2020) gridded rainfall. The benchmark worst droughts were identified considering the extent and severity of drought using the Drought Severity Coverage Index (DSCI). The worst meteorological droughts in June, July, August, and September occurred in 1923, 2002, 1937, and 1907 with a return period of 68, 200, 147, 188 years, respectively. The worst drought in the entire summer monsoon season occurred in 1918, which had a return period of 238 years. The benchmark droughts during June 1923, July 2002, and monsoon 1918 were associated with the warm SST over the equatorial Pacific Ocean. The other two droughts (1937 and 1907) were linked with the off-equatorial warming over the Indo-Pacific region. The estimated DSCI for a 2-500 return period can be used for the drought assessment during the monsoon season in India.

Speakers

16:30-17:00
Discussion
17:00-18:30
Poster session

Chair

Professor Jim Hall FREng

University of Oxford, UK

09:00-09:30
Agriculture and drought - from coping to adapting?

Abstract

Droughts affect a range of economically important sectors but their impacts are usually most evident within agriculture. These impacts are not confined to arid and semi-arid regions, but are increasingly experienced in more temperate and humid regions. Agriculture is a highly heterogenous sector, with differing drought sensitivity and potential drought response options. This presentation will first consider how agriculture is affected by different types of drought and then, using research from Thailand and the UK, consider examples of reactive and adaptive drought responses implemented by farming and non-farming actors. Finally, the presentation will discuss how agriculture can transition to longer-term planning and investment that builds drought resilience through supporting both short-term coping responses and effective adaptation to future droughts.

Speakers

09:30-10:00
Understanding the transgression of global and regional freshwater planetary boundaries

Abstract

Freshwater ecosystems have degraded over the past decades as a result of intense freshwater abstraction. Therefore, environmental flow requirements (EFRs) methods have been proposed to maintain healthy rivers and/or restore river flows. In this study, Dr Pastor and her colleagues used the Variable Monthly Flow method with two thresholds (normal and high) to calculate EFRs on a global scale. They propose a novel method to calculate the transgression of freshwater planetary boundaries by accounting for water deficit with refined spatial (0.5°) and temporal scales: (1) climate deficits in which flow does not meet EFRs due to climate variability/climate change, and (2) anthropogenic deficit caused by water abstractions. Compared to previous assessments, they calculated cumulative monthly water deficit in different types of rivers: intermittent and perennial with the frequency, magnitude and causes of environmental flow (EF) deficits. Results show that EF deficit is highly variable among river basins. Perennial rivers with low flow alteration such as the Amazon showed an EF deficit of 2-12% of the total discharge, and the climate deficit was responsible for up to 75% of the total deficit. In rivers with high seasonality and high water abstractions such as the Indus, the total deficit represents up to 130% of its total discharge, of which 85% is due to abstractions. 

Speakers

10:00-10:30
Causes of Hydrological Drought and the Consequences for Resilience in the Northern Murray-Darling Basin, Australia

Abstract

Climate change modelling projects increases in potential evapotranspiration, notwithstanding projected increases in global land precipitation. This has fundamental implications for managing water within catchments, requiring to sustainably balance water allocations for competing users, especially in semi-arid and arid environments. Using meteorological and hydrological data from gauging stations in the northern Murray-Darling Basin (MDB) of south-eastern Australia, Professor Grafton and his colleagues evaluated the possible causes and consequences of measured reductions in streamflows at Caiwarro (Paroo River) and Wilcannia (Lower Darling River). In conjunction, they analysed fluctuations in waterbird adundance estimated from aerial surveys between 1983 and 2020. They find: (1) drying trends and reduced streamflows at Caiwarro and Wilcannia; (2) streamflow declines at Wilcannia, adjacent to Menindee Lakes, cannot be attributed to climate change alone; (3) waterbird diversity and abundance have declined at Menindee Lakes with streamflow decline and substantially more than the recorded declines at RAMSAR Paroo national wetlands, downstream of Caiwarro; (4) resilience, as measured by resistance and recovery time, of waterbird abundance to droughts is greater in the Paroo national wetlands compared to Menindee Lakes; and (5) reductions in upstream water extractions increase waterbird resilience and the costs of these mitigating measures vary from A$24m to A$75m. 

Speakers

10:30-11:00
Discussion
11:00-11:30
Coffee break
11:30-12:30
Panel discussion: Preparing for and managing droughts

Speakers


Chair

13:30-14:00
The risks of droughts for public water supplies

Abstract

Increasing pressures on water supplies, from climate change and population growth mean that there is an ever-growing need to examine the resilience of public water supplies. Traditional methods for balancing water supply and demand do not explicitly examine system performance during extreme drought events. Analysing the resilience of public water supplies requires dynamical simulation of system performance before, during and after extreme events. The water supply system in England and Wales is very complex, involving multiple catchments, transfers and regulation. System resilience therefore needs to be analysed over broad scales, taking full account of these complex interdependencies. Having not seen major new strategic resource investment since the 1980s, a series of strategic resource options, including major inter-basin transfers and storage reservoirs, are now under consideration. This raises questions about the resilience of these new supplies, in the context of extreme and widespread droughts. This presentation will explore the limits to adaptation in this system, when multiple strategic water resource options are used in combination. Under what conditions will these new strategic options cease to provide resilient water supplies, and how can they be operated to enhance resilience? The analysis will make use of a coupled system of regional climate model simulations, national hydrological modelling and national water resource system simulation modelling.

Speakers

Professor Jim Hall FREng

University of Oxford, UK

14:00-14:30
The economics of managing water crises

Abstract

The growing risk of water crises, including drought, is one of the greatest challenges in the coming decades. Averting such crises will be especially daunting, given that they are just as much a failure of water management as a result of scarcity. At the heart of global water mismanagement is the persistent underpricing of water. The increasing environmental and social costs associated with freshwater scarcity are not routinely reflected in markets. Nor have we developed adequate policies and institutions to handle these costs. This creates perverse incentives that fail to balance water use with supply, protect freshwater ecosystems and support necessary technological innovations. However, drought is proving to be a catalyst for governance and policy reform, and steps can be taken to overcome the underpricing of water. Several examples are explored to illustrate the problem and how to overcome it. They include employing water markets and trades to facilitate water conservation and re-allocation, increasing cost-effective delivery of clean water and sanitation in developing countries, and rationalising irrigation and other agricultural subsidies that lead to over-use and pollution of water. A comprehensive strategy for water-saving innovation is also discussed.

Speakers

14:30-15:00
Discussion
15:00-15:30
Tea break
15:30-16:30
Panel discussion: concluding remarks and future directions

Speakers

Professor Gabriele Hegerl FRS

University of Edinburgh, UK

16:30-17:00
Closing remarks

Abstract

 

Speakers

Professor Jim Hall FREng

University of Oxford, UK

Professor Gabriele Hegerl FRS

University of Edinburgh, UK