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A Forum for Discussion
A Forum for Discussion
Stephen Briggs (ESA) The Importance of Space Observations for Climate
T
he history of recorded observations of climate and climate phenomena goes back more than three hundred years. The first Astronomer Royal, John Flamsteed, and the Italian astronomer Giovanni Cassini recorded sunspot numbers in the late seventeenth century. These were later used to reconstruct the long-period variability of the sun, giving rise to the “Maunder Minimum”of solar activity. Even today these observations have an importance in the understanding of long-term climate change. A key meeting was that convened by Lieutenant Maury of the US Navy in Brussels in 1853, for the first time creating an international cooperation in weather and climate observations. Captain Robert Fitzroy, RN, had already begun the series of routine observations in the UK which gave rise to the UK Met Office in 1854 as a service to mariners. Following the Brussels Conference, the International Weather Organisation was created in 1873, evolving in 1951 into the World Meteorological Organisation that coordinates climate observations to the present day. Thereafter, a major step forward was establishment of the Global Climate Observing System (GCOS) in 1992. GCOS is charged with the specification of the observations needed for climate studies, and for advocating for these to be made by a variety of different bodies worldwide. In its second implementation plan in 2004 GCOS identified the concept of Essential Climate Variables, at the heart of today’s climate observations. GCOS has identified some fifty ECVs, roughly equally divided across the three physical domains of atmosphere, oceans and land. GCOS formally reports its assessment of the current status of the observing system for climate each year to the Conference of the Parties of the United Nations Framework Convention on Climate Change (UNFCCC), and systematic observations are specifically cited in Articles 4 and 5 of the Convention since its inception in 1992. Of the 50 ECVs, over half are derived directly from Earth observing satellites, while of the remainder about half have a major dependence on satellite data. Less than a quarter are based solely on in situ measurements—soil carbon, deep ocean temperature are examples. As a result satellites are critical to climate observations, and the scientific understanding, modelling and prediction of climate described by the Intergovernmental Panel on Climate Change (IPCC) Working Group I in its last Assessment Report (AR5) is largely founded on satellite observations. In preparation for the UNFCCC CoP-21 later this year, GCOS is preparing a comprehensive report of the status of climate observations. Following on from the Status Report a further revised Implementation Plan for GCOS will be presented to the UNFCCC Parties at the CoP-22 in November 2016. This will also detail the use of satellite observations for climate adaptation and mitigation, as well as looking at the needs of the other Rio Conventions. A specific Satellite Supplement to the last two GCOS Implementation Plans has been prepared by GCOS. This sets out the specific needs of the observing system to be fulfilled by satellite observations and has allowed a coherent and comprehensive response to be formulated by space agencies world2
wide. The Committee on Earth Observation Satellites (CEOS) coordinates worldwide Earth observation from satellites and responded by delivering to GCOS a wide-ranging report of its actions in response to its specific needs. Meteorological satellites have been making atmospheric measurements primarily for weather forecasting for over 50 years, and many are directly relevant to climate modelling. Originally focused on atmospheric temperature, pressure and humidity, they have gradually expanded to include atmospheric composition and to measurements of ocean and land parameters. More recently, research space agencies from across the world have further expanded the range of observed parameters to encompass the majority of the ECVs set out by GCOS. Critical observations made from satellites now include arctic sea ice extent and thickness (concentration), sea surface temperature, glacier extent and change, Greenland and Antarctic ice sheet mass balance, global land cover type, albedo, aerosol concentration, ocean biological activity, vegetation processes through measurement of photo-synthetically active radiation and vegetation structure, and so on. And, of course, all these as disaggregated, geospatially referenced data sets. They form the basis for the description of physical processes in the climate system, for example the energy and water cycles. Climate models, and hence our understanding of what may be the consequences of humanity’s (mis)treatment of our home planet, are thus critically dependent on satellite observations. But that is not where the contribution of satellites stops. The way that humankind may adapt to a changed climate, and how it may mitigate its effect on the climate system—the other two aspects of the IPCC Assessments—are also informed by satellite data. Mitigation of emissions, aside from reduction of fossil fuel combustion, is largely based on the modification of land use, from practices which emit greenhouse gases to those which absorb them, by reforestation for example. Observations of land use change are hence critical. Optimised siting of renewable energy sources (solar, wind or tidal) are also informed by satellite observations and the derived parameter fields. Adapting to and managing the impacts of climate change requires an even greater range of satellite data. For many years agencies have collaborated through an international Charter to provide easy, free access to imagery in the aftermath of natural disasters. Calls on this Charter have been increasing as such events multiply. In addition, adaptation to a changed climate will also need the support of climate services ranging from advice on better flood management and modified agricultural practices to improved coastal defence, characterization of disease vectors and other health threats, all dependent on access to accurate geospatial data about the physical environment coming from satellite systems. There is one further important benefit satellite observations of climate can bestow on us. The present discussion on climate in the public domain is less useful than it might be as a consequence of the lack of awareness and understanding, entirely reasonable, by the public of the scale and results of climate change. They have been confronted with a single number—surface temperature—which is for many reasons a very poor indicator of climate change. Precisely because it is such a poor indicator (it characterizes only a tiny fraction, less than 1%, of the total increase in energy in the Earth system), it gives unclear messages which are either accidentally or deliberately misinterpreted as being indicative of lack of climate change, with associated calumny heaped on scientists as a result. There are much better indicators for the public—not only surface temperature, but sea level, arctic ice extent, atmospheric carbon dioxide concentration, ocean heat content, ice sheet mass balance—mostly derived from satellite data which could provide a much more coherent, consistent and more easily understood dashboard of climate change for the public. We should ensure that these measurements are made freely and openly available in a way which cannot be either accidentally or deliberately misunderstood. The crucial role of satellites in understanding climate change will then be supplemented by their role in communicating its consequences. It may even one day influence politicians. 3
Stephen Briggs (ESA) The Importance of Space Observations for Climate
T
he history of recorded observations of climate and climate phenomena goes back more than three hundred years. The first Astronomer Royal, John Flamsteed, and the Italian astronomer Giovanni Cassini recorded sunspot numbers in the late seventeenth century. These were later used to reconstruct the long-period variability of the sun, giving rise to the “Maunder Minimum”of solar activity. Even today these observations have an importance in the understanding of long-term climate change. A key meeting was that convened by Lieutenant Maury of the US Navy in Brussels in 1853, for the first time creating an international cooperation in weather and climate observations. Captain Robert Fitzroy, RN, had already begun the series of routine observations in the UK which gave rise to the UK Met Office in 1854 as a service to mariners. Following the Brussels Conference, the International Weather Organisation was created in 1873, evolving in 1951 into the World Meteorological Organisation that coordinates climate observations to the present day. Thereafter, a major step forward was establishment of the Global Climate Observing System (GCOS) in 1992. GCOS is charged with the specification of the observations needed for climate studies, and for advocating for these to be made by a variety of different bodies worldwide. In its second implementation plan in 2004 GCOS identified the concept of Essential Climate Variables, at the heart of today’s climate observations. GCOS has identified some fifty ECVs, roughly equally divided across the three physical domains of atmosphere, oceans and land. GCOS formally reports its assessment of the current status of the observing system for climate each year to the Conference of the Parties of the United Nations Framework Convention on Climate Change (UNFCCC), and systematic observations are specifically cited in Articles 4 and 5 of the Convention since its inception in 1992. Of the 50 ECVs, over half are derived directly from Earth observing satellites, while of the remainder about half have a major dependence on satellite data. Less than a quarter are based solely on in situ measurements—soil carbon, deep ocean temperature are examples. As a result satellites are critical to climate observations, and the scientific understanding, modelling and prediction of climate described by the Intergovernmental Panel on Climate Change (IPCC) Working Group I in its last Assessment Report (AR5) is largely founded on satellite observations. In preparation for the UNFCCC CoP-21 later this year, GCOS is preparing a comprehensive report of the status of climate observations. Following on from the Status Report a further revised Implementation Plan for GCOS will be presented to the UNFCCC Parties at the CoP-22 in November 2016. This will also detail the use of satellite observations for climate adaptation and mitigation, as well as looking at the needs of the other Rio Conventions. A specific Satellite Supplement to the last two GCOS Implementation Plans has been prepared by GCOS. This sets out the specific needs of the observing system to be fulfilled by satellite observations and has allowed a coherent and comprehensive response to be formulated by space agencies world2
wide. The Committee on Earth Observation Satellites (CEOS) coordinates worldwide Earth observation from satellites and responded by delivering to GCOS a wide-ranging report of its actions in response to its specific needs. Meteorological satellites have been making atmospheric measurements primarily for weather forecasting for over 50 years, and many are directly relevant to climate modelling. Originally focused on atmospheric temperature, pressure and humidity, they have gradually expanded to include atmospheric composition and to measurements of ocean and land parameters. More recently, research space agencies from across the world have further expanded the range of observed parameters to encompass the majority of the ECVs set out by GCOS. Critical observations made from satellites now include arctic sea ice extent and thickness (concentration), sea surface temperature, glacier extent and change, Greenland and Antarctic ice sheet mass balance, global land cover type, albedo, aerosol concentration, ocean biological activity, vegetation processes through measurement of photo-synthetically active radiation and vegetation structure, and so on. And, of course, all these as disaggregated, geospatially referenced data sets. They form the basis for the description of physical processes in the climate system, for example the energy and water cycles. Climate models, and hence our understanding of what may be the consequences of humanity’s (mis)treatment of our home planet, are thus critically dependent on satellite observations. But that is not where the contribution of satellites stops. The way that humankind may adapt to a changed climate, and how it may mitigate its effect on the climate system—the other two aspects of the IPCC Assessments—are also informed by satellite data. Mitigation of emissions, aside from reduction of fossil fuel combustion, is largely based on the modification of land use, from practices which emit greenhouse gases to those which absorb them, by reforestation for example. Observations of land use change are hence critical. Optimised siting of renewable energy sources (solar, wind or tidal) are also informed by satellite observations and the derived parameter fields. Adapting to and managing the impacts of climate change requires an even greater range of satellite data. For many years agencies have collaborated through an international Charter to provide easy, free access to imagery in the aftermath of natural disasters. Calls on this Charter have been increasing as such events multiply. In addition, adaptation to a changed climate will also need the support of climate services ranging from advice on better flood management and modified agricultural practices to improved coastal defence, characterization of disease vectors and other health threats, all dependent on access to accurate geospatial data about the physical environment coming from satellite systems. There is one further important benefit satellite observations of climate can bestow on us. The present discussion on climate in the public domain is less useful than it might be as a consequence of the lack of awareness and understanding, entirely reasonable, by the public of the scale and results of climate change. They have been confronted with a single number—surface temperature—which is for many reasons a very poor indicator of climate change. Precisely because it is such a poor indicator (it characterizes only a tiny fraction, less than 1%, of the total increase in energy in the Earth system), it gives unclear messages which are either accidentally or deliberately misinterpreted as being indicative of lack of climate change, with associated calumny heaped on scientists as a result. There are much better indicators for the public—not only surface temperature, but sea level, arctic ice extent, atmospheric carbon dioxide concentration, ocean heat content, ice sheet mass balance—mostly derived from satellite data which could provide a much more coherent, consistent and more easily understood dashboard of climate change for the public. We should ensure that these measurements are made freely and openly available in a way which cannot be either accidentally or deliberately misunderstood. The crucial role of satellites in understanding climate change will then be supplemented by their role in communicating its consequences. It may even one day influence politicians. 3