Franzke C.,British Antarctic Survey
Journal of Climate | Year: 2012
This study investigates the significance of trends of four temperature time series-Central England Temperature (CET), Stockholm, Faraday-Vernadsky, and Alert. First the robustness and accuracy of various trend detection methods are examined: ordinary least squares, robust and generalized linear model regression, Ensemble Empirical Mode Decomposition (EEMD), and wavelets. It is found in tests with surrogate data that these trend detection methods are robust for nonlinear trends, superposed autocorrelated fluctuations, and non-Gaussian fluctuations. An analysis of the four temperature time series reveals evidence of long-range dependence (LRD) and nonlinear warming trends. The significance of these trends is tested against climate noise. Three different methods are used to generate climate noise: (i) a short-range-dependent autoregressive process of first order [AR(1)], (ii) an LRD model, and (iii) phase scrambling. It is found that the ability to distinguish the observed warming trend from stochastic trends depends on the model representing the background climate variability. Strong evidence is found of a significant warming trend at Faraday-Vernadsky that cannot be explained by any of the three null models. The authors find moderate evidence of warming trends for the Stockholm and CET time series that are significant against AR(1) and phase scrambling but not the LRD model. This suggests that the degree of significance of climate trends depends on the null model used to represent intrinsic climate variability. This study highlights that in statistical trend tests, more than just one simple null model of intrinsic climate variability should be used. This allows one to better gauge the degree of confidence to have in the significance of trends. © 2012 American Meteorological Society.
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 322.57K | Year: 2016
The thermosphere is the uppermost layer of our atmosphere at the edge of space (85 to 1000 km altitude). Within this region orbit thousands of satellites worth billions of pounds that provide essential modern services including satnav, satcomms, and remote sensing. There are also many thousands more orbiting pieces of man-made space debris which present a significant risk to operational satellites because of the chance of collision. We have now passed a tipping point where the increase in debris from collisions exceeds losses, leading to a net growth of the space debris population and thus ever-increasing risk of collisions. Short- and long-term predictions of satellite and debris trajectories are vital to avoid the destruction of satellites in low-Earth orbit. A major factor limiting factor is knowing the density of the thermosphere, which can vary by up to 800% during extreme times. The variability is due to effects in near-Earth space from disturbances on the Sun, collectively called space weather. In the polar regions, where there is the greatest concentration of satellites, the largest uncertainties in thermospheric density arise from Joule heating. This is caused by collisions between electrically-charged and neutral particles in the thermosphere, driven by space weather. Crucially, we have yet to properly understand when and where Joule heating will occur and how predictable it is. Accurate models and prediction of Joule heating are vital to safeguard the space assets on which modern society depends. In this project we will develop a better understanding of Joule heating by analysing more than a decade of data from two major international polar instrument networks. We will use a statistical method developed in meteorology called Empirical Orthogonal Function (EOF) analysis, which is capable of uncovering the underlying patterns in a large, noisy data set. In this way we will both resolve the Joule heating in unprecedented detail and separate it into patterns which depend to greater or lesser degrees on the solar sources of space weather. Since these sources can be observed before they cause space weather at Earth, this will allow us to quantify the limits of predictability of the Joule heating. By then assessing the relationship between the Joule heating and satellite trajectories, this will allow us to describe which orbital paths are most at risk from space weather.
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 1.36M | Year: 2016
Major changes are occurring across the North Atlantic climate system: in ocean and atmosphere temperatures and circulation, in sea ice thickness and extent, and in key atmospheric constituents such as ozone, methane and particles known as aerosols. Many observed changes are unprecedented in instrumental records. Changes in the North Atlantic directly affect the UKs climate, weather and air quality, with major economic impacts on agriculture, fisheries, water, energy, transport and health. The North Atlantic also has global importance, since changes here drive changes in climate, hazardous weather and air quality further afield, such as in North America, Africa and Asia. ACSIS is a 5 year strategic research programme that brings together and exploits a wide range of capabilities and expertise in the UK environmental science community. Its goal is to enhance the UKs capability to detect, attribute (i.e. explain the causes of) and predict changes in the North Atlantic Climate System. ACSIS will deliver new understanding of the NA climate system by integrating new and old observations of atmospheric physics and chemistry, of the ocean state and of Arctic Ice. The observations will be complemented by detailed data analysis and numerical simulations. Observations will come from existing networks, from NERCs own observational sites in the North Atlantic, and from space. Seasonal surveys using the NCAS FAAM aeroplane will further enhance our observational strategy. A key dimension of the observational opportunity is that data records of sufficient length, for multiple variables, are becoming available for the first time. The modelling component will involve core numerical simulations with cutting-edge atmosphere, ocean, sea ice, chemistry and aerosol models using the latest parameterizations and unprecedented spatial detail, as well as bespoke experiments to investigate specific time periods or to explore and explain particular observations. ACSIS will provide advances in understanding and predicting changes in the NA climate system that can be exploited to assess the impact of these changes on the UK and other countries - for example in terms of the consequences for hazardous weather risk, the environment and businesses. ACSIS outputs will also inform policy on climate change adaptation and air quality.
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 409.87K | Year: 2017
The surface ocean is home to billions of microscopic plants called phytoplankton which produce organic matter in the surface ocean using sunlight and carbon dioxide. When they die they sink, taking this carbon into the deep ocean, where it is stored on timescales of hundreds to thousands of years, which helps keep our climate the way it is today. The size of the effect they have on our climate is linked to how deep they sink before they dissolve - the deeper they sink, the more carbon is stored. This sinking carbon also provides food to the animals living in the oceans deep, dark twilight zone. Computer models can help us predict how future changes in greenhouse gas emissions might change this ocean carbon store. Current models however struggle with making these predictions. This is partly because until recently we havent even been able to answer the basic question Is there enough food for all the animals living in the twilight zone?. But in a breakthrough this year we used new technology and new theory to show that there is indeed enough food. So now we can move on to asking what controls how deep the carbon sinks. There are lots of factors which might affect how deep the material sinks but at the moment we cant be sure which ones are important. In this project we will make oceanographic expeditions to two different places to test how these different factors affect carbon storage in the deep ocean. We will measure the carbon sinking into the twilight zone and the biological processes going on within it. Then we will determine if the systems are balanced - in other words, what goes in, should come out again. We will then write equations linking all the parts of the system together and analyse them to make them more simple. At the same time we will test whether the simple equations are still useful by seeing if they produce good global maps of ocean properties for which we have lots of data. Finally, when we are happy that our new equations are doing a good job we will use them in a computer model to predict the future store of carbon in the ocean.
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 1.01M | Year: 2016
Global climate change is one of the leading environmental threats facing mankind. To develop appropriate mitigation and adaptation strategies requires accurate projections of the future state of the Earths climate. To address this, the research community have developed Global Climate Models (GCMs) that describe the main physical processes in the coupled climate system. These mathematical-computer models are integrated forwards in simulated time, from a pre-industrial period(before ~1850) to present-day, forced by observed estimates of key greenhouse gases (e.g. carbon dioxide, methane, ozone), aerosols and land-use. The models are then continued into the simulated future forced by a range of greenhouse gas, aerosol and land-use scenarios representing plausible future socio-economic development pathways. Each of the time-evolving model future climates are then compared to the pre-industrial and present-day climates from the same model. This analysis results in an ensemble of climate change estimates, linked to each of the applied development pathways, that can be used to assess potential socio-economic and ecological impacts and aid in the development of climate change mitigation and adaptation policies. GCMs have recently been further developed into Earth system models (ESMs). A key difference between ESMs and GCMs is the former include an interactive description of the global carbon cycle. Climate change is primarily driven by human emissions of carbon dioxide which traps a fraction of the Earths emitted radiation in the atmosphere, warming it and the Earths surface. This direct warming from increasing carbon dioxide can be amplified or damped by various feedbacks in the climate system (e.g. involving water vapour, clouds or sea-ice). A key determinant of the climate change impact of human-emitted carbon dioxide is how much of the emitted gas actually stays in the atmosphere where it can interact with the Earths emitted radiation. Presently, around 50% of the carbon dioxide emitted by humans stays in the atmosphere, the remaining 50% being taken up, in roughly equal measures, by the terrestrial biosphere and the world oceans. There is increasing evidence to suggest the efficiency of these natural carbon reservoirs in absorbing human-emitted carbon dioxide may change in the future, being sensitive to both the concentration of carbon dioxide in the Earth system and to the induced climate change. A reduction in the uptake efficiency of Earths natural carbon reservoirs would result in a larger fraction of emitted carbon dioxide remaining in the atmosphere and thereby a larger climate change (warming) for a given cumulative emission of carbon dioxide. To address the need to simulate both the changing global climate and the carbon cycle response to a changing climate and changing atmospheric composition, we are developing the 1st UK Earth system model, based on the core physical GCM, HadGEM3, developed at the Met Office. This development is a major collaboration between NERC centres and the Met Office, integrating a large body of core research and development into a single, world-leading ESM. This proposal aims to secure the NERC funding to maintain this collaboration. The project will support the final development and community release of the 1st UKESM models, as well as application of these models to a range of collaborative science experiments carried out at the international level to support the IPCC AR6. The project has a major emphasis on evaluating the full range of climate and biogeochemical processes and interactions simulated by UKESM1 models with an aim to increase confidence in future projections made with the models. The project will also generate and analyse a suite of such projections and deliver a set of robust estimates of Earth system change to UK government, business and the public. Finally, the project will initiate long-term development of a 2nd version of the UKESM model, for release ~2023.
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 7.09M | Year: 2016
Climate change is one of the most urgent issues facing humanity and life on Earth. Better predictions of future climate change are needed, so that measures to reduce its impact and cope with its effects can be put in place. However, improving these predictions requires better knowledge of how the global climate system functions, and this knowledge is currently incomplete. A critical gap concerns understanding of the uptake of heat and carbon by the oceans. Over 90% of the extra heat now present in the Earth System because of global warming has entered the ocean, with strong increases in both the upper and deep ocean apparent since the 1970s. Further, the global ocean is the largest reservoir of carbon in the climate system, and has absorbed nearly one-third of the extra carbon emissions produced since the industrial revolution. Climate change in the atmosphere is strongly moderated by these processes, and would be dramatically greater without them. The Southern Ocean - the vast ocean that encircles Antarctica - is critically important in this regard. Because of the nature of its circulation, its physical and chemical properties, and its connections with the rest of the globe, it accounts for around half of the oceanic uptake of carbon, and around three-quarters of the heat uptake. However, because of its remoteness and hostile environment, with stormy seas, heavy sea ice in places, and long periods of darkness in winter, the Southern Ocean is also the least-measured and least-understood ocean in the world. One consequence of this lack of understanding is that the representations of the Southern Ocean in many of the models used to create future climate projections are not fit for purpose. Our project, Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA), represents a linking together of many of the major environmental research institutes in the UK, who will work with national and international partners to address these issues. We propose a combination of data collection, novel analyses and computer simulations to radically improve our ability to measure, understand and predict the circulation and role in global climate of the Southern Ocean. Data collection will include major ship-based expeditions across the Atlantic sector of the Southern Ocean to determine the basin-scale transports of heat and carbon in all the different ocean layers (near-surface, intermediate, abyssal). It will include the use of novel technology and unmanned vehicles to collect data over much longer periods and much greater areas than ships alone could allow, and flights with research aircraft to determine climatically-important transfers of heat and carbon between the atmosphere and ocean in all different conditions of sea ice. Informed by the new understanding that these field campaigns will produce, improvements to ocean models will be proposed and tested, and the improvements delivered to climate modellers so that better future projections can be produced. It is clear that these developments are required urgently - the benefits to be gained by improving climate prediction are difficult to overstate, with more effective strategies for dealing with climate change becoming feasible, and better planning assumptions made possible for industry, commerce and other sectors. The value of the Southern Ocean carbon sink was recently estimated to be in the trillions of dollars, but with uncertainty in the billions concerning how it will change in future: narrowing this uncertainty is thus a strong economic priority, as well as a scientific and societal one.
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 389.46K | Year: 2016
The main goals of this proposal are to assess the evolutionary history of Colobanthus quitensis in Antarctica and southern South America by evaluating: (i) how its genetic diversity is distributed within and among populations, (ii) how historical processes have influenced the contemporary distribution of C. quitensis across its southern range of distribution, and (iii) whether geographical patterns of genetic variation are consistent with the diversity of microflora and their symbiotic effects. These predictions will be tested using experimental approaches as well as population genetic and phylogeographic analyses. This research proposal will shed fundamental new light on the evolutionary history of the flora between South America and the Antarctica.
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 2.48M | Year: 2015
That our planet is warming is undeniable. Recent increases in greenhouse gas concentrations have seen an associated warming of the atmosphere and oceans, a reduction in the total amount of snow and ice and a rise in sea level of approximately 3 mm/year. Although the precise rate of future temperature rise may be uncertain, there is little doubt that it will increase. In response to a warmer climate, large areas of the Antarctic Ice Sheet could become unstable, resulting in sudden and permanent loss of ice. Indeed for one relatively well-studied region, the Amundsen Sea Sector, this may already be underway. However, our understanding of the processes, the likelihood of collapse and the potential impact on sea-level remains poor, especially in the very different climatic regime of the Weddell Sector. This project aims to address what will happen in the near-future to a region that spans one fifth of Antarctica and the impact changes here could have on global sea-level by the end of this century. We aim to do this in three stages: We will study and understand the intricate relationships between the atmosphere, the ocean and the ice sheet in the important Weddell sector of Antarctica, which contains Filchner Ice Shelf and its catchment basins. We will determine how the atmosphere determines the ocean conditions, and how these in turn determine the melting at the base of the ice shelf. In a carefully designed field campaign we will collect data both to improve the way the models work, and also to validate their results. This first stage will yield a system of models that gives a detailed representation of the physical processes currently at work, and by using the natural variability in the system we will determine the sensitivity to change of each linked process. The next step is to force the boundaries of our modelled system with the best available estimate of the atmospheric and oceanographic properties expected over the 21st century. We will then be in a position to determine how the ocean conditions beneath the ice shelf will change, together with the rate of melting at the ice shelf base. As the melt rate changes, so will the ice shelf geometry: we will determine how the rate of ice flow from the continent responds to these changes, and its impact on sea-level rise. In the final stage we will widen the scope of the study from our large, yet still regional area, to a global context. The models to be used in the first two steps, (atmosphere, ocean and ice) are high resolution, state-of-the-art but limited-area models. We will work with our Project Partner, the Met Office Hadley Centre (MO), to incorporate our improved understanding of processes and their sensitivities within the next generation of global earth-system predictive models. Finally, we will assess the reliability of our predictions. This will be done first by ensuring consistency between the different regional models, run both within the project and by our project partners at the Alfred Wegener Institute (AWI) in Germany. We will then use a limited ensemble of runs of the new generation of MO coupled climate models to quantify the uncertainty in our predictions of the contribution of the Antarctic Ice Sheet to sea level change. The future contribution of the Antarctic Ice Sheet to sea level rise remains the least well constrained component in the budget. By bringing together from across the community leading experts in polar meteorology, oceanography, ice-ocean interaction, glaciology and model uncertainty, this project will provide the largest single improvement in the prediction of future sea level change. New observations and data are essential, but expensive. Rather than using costly commercially-available infrastructure, AWI and NERC will share the logistic burden with the project delivering excellent value as a result.
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 630.66K | Year: 2016
The ozone layer shields all land-based life forms from harmful ultraviolet radiation; and indirectly influences the climate at the Earths surface, including temperature and winds, particularly near the poles. Man-made halocarbons, used for example in refrigerators and spray cans, were released to the atmosphere and have caused significant destruction of the ozone layer since the late 1970s, especially above Antarctica during spring-time. Because the use of many halocarbons was banned by the 1989 Montreal Protocol, the ozone layer is expected to recover to the conditions of the 1960s and early 1970s within this century. However, the thickness of the ozone layer is also influenced by natural causes, which are less well understood and which make predictions of future ozone and climate less certain. Natural causes include variations in the suns activity, volcanic eruptions, release of biogenic halocarbons and atmospheric circulation. Currently there is very little information on the natural variability of the ozone layer over historic time scales, i.e. before direct observations started in the early 20th century. However, understanding the natural variability of the ozone layer and the underlying causes is necessary to evaluate the effectiveness of climate and ozone policy options. It is also necessary in order to improve predictions of ground level UV radiation, which is recognized as an environmental carcinogen and a major concern for human health. One way to go back in time beyond the era of modern measurements is the use of proxies measured in polar ice cores. Apart from a recently proposed biomarker there are no quantitative proxies of past UV radiation. Here we propose to measure the isotopes of nitrogen and oxygen in the nitrate ion in polar ice to reconstruct past ultraviolet radiation and therefore the ozone layer. Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. In the very dry regions of inner Antarctica snow is exposed to sunlight for many months before being buried by snowfall. During that exposure the nitrate in the snow is decomposed by solar UV radiation; during that process the heavier nitrogen isotopes in nitrate are observed to stay preferentially in the snow, whereas the lighter ones escape to the atmosphere above. That fractionation depends on the wavelength and duration of the UV radiation. We hypothesize that once the nitrate in snow is buried at depth, it preserves an isotopic fingerprint of down-welling UV radiation and therefore of the thickness of the ozone layer. We propose to collect a shallow ice core from East Antarctic Plateau, where low accumulation rates prevail, to develop and apply a new ice core proxy based on the stable isotopes of nitrate, to constrain trends in the ozone layer above Antarctica over the last 1kyr. To do this, we will calibrate the ice core signal with observations of the ozone layer above Antarctica since the 1950s, and then extrapolate that relationship to the more distant past. Using numerical models we will investigate the underlying causes of the ice core based reconstruction of past variability in the ozone layer. Particular questions we will attempt to answer include: has stratospheric ozone changed in the past; and how did solar variability, natural emissions of halocarbons, or volcanic eruptions contribute to the reconstructed trends?
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 440.90K | Year: 2016
Climate change is one of the leading global challenges facing society and the planet. Predicting how the climate will change as human activities lead to emission of more greenhouse gases is a global scientific challenge for climate scientists. We use models of the climate to make predictions. Because of limitations in computing power, and because of gaps in our understanding of the climate, these models are not perfect. Predictions from the models are, therefore, also not perfect. We are faced by the huge challenge of extracting robust information from climate models about how real-world climate will change in the future under specified scenarios of different greenhouse gas emissions. Such projections are central to leading climate change assessments, such as those produced by the Intergovernmental Panel on Climate Change (IPCC). This project will provide a step-change in the ability of climate scientists to produce robust projections of climate change and to quantify the uncertainties in projections. A new framework will be developed that combines information from models, observations and our basic understanding of climate with modern statistical techniques to produce projections. This new framework will be applied to three important climate regimes of Earth: tropical and subtropical temperature and precipitation change; middle latitude cyclones and anti-cyclones; and polar temperature and sea-ice changes. We will bring together leading UK scientists (many are IPCC authors) from the Universities of Exeter, Reading, Oxford and East Anglia, and the Met Office, to address this grand challenge in climate science. We aim to precipitate a cultural shift that unifies diverse approaches from techniques to understand climate process and statistical methods and consolidate the UKs position as a world-leading centre for climate projection science.