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Satellite Observations in Support of Climate Challenges
Counting Carbon
The Big Thaw
Sea Level Rise
Water Security
Land Surface Change
Energy Resource Management

Earth's Lights by night

As explained in Part I, the IPCC noted in 2007 that changes in atmospheric concentrations of greenhouse gases and aerosols, land cover and solar radiation alter the energy balance of the climate system. Global greenhouse gas emissions due to human activities have grown since pre-industrial times, with an increase of 70% between 1970 and 2004. The IPCC concluded that “most of the observed increase in globally averaged temperatures since the mid-20th century is very likely (over 90% probability) due to the observed increase in anthropogenic (man-made) greenhouse gas concentrations”.

The most important of the greenhouse gases associated with global warming is carbon dioxide (CO2). Other important greenhouse gases include methane (CH4), nitrous oxide (N2O), ozone (O3), and chlorofluorocarbons (CFCs). Global atmospheric concentrations of CO2, CH4 and N2O have increased markedly as a result of human activities since 1750 and now far exceed the pre-industrial values determined from ice cores that span many thousands of years.

Global increases in CO2 concentrations are due primarily to the burning of fossil fuels such as oil, gasoline, natural gas and coal, with land use change providing another significant but smaller contribution. It is very likely that the observed increase in CH4 concentration is predominantly due to agriculture and fossil fuel use. Methane growth rates have declined since the early 1990s, consistent with total emission (sum of anthropogenic and natural sources) being nearly constant during this period. The increase in N2O concentration is primarily due to agriculture.

Future projections regarding the changing composition of the Earth’s atmosphere and the impact this will likely have on its climate, have been briefly outlined in Part I of this document.

The International Response
The adoption of the United Nations Framework Convention on Climate Change (UNFCCC) in 1992 was a major step forward in tackling the problem of global warming. Yet, as greenhouse gas emission levels continued to rise around the world, it became increasingly evident that a firm and binding commitment by developed countries to reduce emissions could send a signal strong enough to convince businesses, communities and individuals to act on climate change. As a result, UNFCCC member countries began negotiations on a Protocol, an international agreement linked to the existing Treaty, but standing on its own.

After two and a half years of intense negotiations, the Kyoto Protocol was adopted at the third Conference of the Parties to the UNFCCC (COP 3) in Kyoto, Japan, on 11 December 1997. The Protocol shares the objectives and institutions of the Convention. The major distinction between the two, however, is that while the Convention encouraged developed countries to stabilise greenhouse gas emissions, the Protocol commits them to do so.

Fossil fuel emissions and deforestation play major roles in climate change
Because it will affect virtually all major sectors of the economy, the Kyoto Protocol is considered to be the most far-reaching agreement on environment and sustainable development ever adopted. However, any treaty not only has to be effective in tackling a complicated worldwide problem, it must also be politically acceptable.

Most of the world’s countries eventually agreed to the Protocol, but some nations chose not to ratify it. The Kyoto Protocol entered into force on 16 February 2005 and by early 2008 it had been ratified by 174 states.

The Protocol requires developed countries to reduce their greenhouse gas emissions below levels specified for each of them in the UN Treaty. These targets must be met within a five-year time frame between 2008 and 2012, and add up to a cut in greenhouse gas emissions of at least 5% against the baseline of 1990. Review and enforcement of these commitments are carried out by United Nations-based bodies. The Protocol places a heavier burden on developed nations under the principle of “common but differe ntiated responsibilities”. This has two main reasons. Firstly, those countries can more easily pay the cost of cutting emissions. Secondly, developed countries have historically contributed more to the problem by emitting larger amounts of greenhouse gases per person than developing countries.

The Kyoto Protocol sets limits on the emission of six main greenhouse gases:

— carbon dioxide (CO2);

— methane (CH4);

— nitrous oxide (N2O);

— hydrofluorocarbons (HFCs);

— perfluorocarbons (PFCs);

— sulphur hexafluoride (SF6).

Some specified activities that emit or remove carbon dioxide from the atmosphere are also covered in the land use change and forestry sector (namely, afforestation, deforestation and reforestation). All changes in emissions and in removals by so-called ‘sinks’ (absorbers) are considered equivalent for accounting purposes. The Protocol also establishes three innovative mechanisms, known as ‘joint implementation’, ‘emissions trading’ and the ‘clean development mechanism’. These are designed to help Parties reduce the costs of meeting their emissions targets by achieving or acquiring emission reductions more cheaply in other countries than at home. The clean development mechanism also aims to assist developing countries to achieve sustainable development by promoting environmentally-friendly investment in their economies by governments and businesses from industrialised countries.

The Role of Satellite Earth Observations
For mitigation and adaptation to be effective, governments and the private sector need information about past and current climate conditions, including their variability and extremes, as well as sound projections of future conditions – not only on an annual basis but for many decades into the future.

Satellites already deliver global estimates of greenhous gas concentrations in our atmosphere
Such climate projections depend on the same information for their development and testing. The World Climate Research Programme (WCRP) was established in 1980 to coordinate international research in this domain, in order to determine the extent to which climate can be predicted and the extent of human influence on climate.

The climate system responds to both external forcings and to perturbations of internal processes. This means that it is important to be able to track climate change and variability in such a way that causes can be determined, trends and variability predicted, and appropriate adaptation and mitigation strategies defined for implementation.

As noted in Part I, the Global Climate Observing System (GCOS) prepared an Implementation Plan for the global observing system for climate in 2004, in response to a request from UNFCCC. This Plan, if fully implemented by the Parties to the UNFCCC, both individually and collectively, will provide the global observations of the Essential Climate Variables and their associated products that will assist the Parties to meet their responsibilities under the UNFCCC. In addition, it will provide many of the essential observations required by the World Climate Research Programme (WCRP) and IPCC.

CEOS, as the primary international forum for coordination of space-based Earth observations, responded by submitting to the UNFCCC its plan (comprising over 50 different actions) to help satellites deliver up to 25 of the 45 Essential Climate Variables defined by GCOS. Of the many and varied global observing systems contributing to climate data collection (including instruments at ground stations, on ships, buoys, floats, ocean profilers, balloons and aircraft), Earth observation satellites providing global coverage and well calibrated measurements will become “the single most important contribution to global observations for climate”. Since the dominant influence on future greenhouse gas trends is widely agreed to be the emission of CO2 from fossil fuel burning, improved observation and understanding of the global carbon cycle is one of priorities for the forthcoming decades.
Japan's GOSAT provides greenhouse gas monitoring capabilities. (credit:JAXA)

Observing the Carbon Cycle
The global carbon cycle spans the three major components of the Earth System: the atmosphere, oceans and land. In each domain, large pools of readily exchangeable carbon are stored in various ways (‘pools’) in the ocean and on the land surface. Large amounts of carbon (in source or sink ‘fluxes’) are transferred between the pools over various time periods, from daily to annual and much longer. Although some of the fluxes are very large, the net change over a given time period need not be. For many centuries prior to the Industrial Revolution, the carbon pools were more or less in equilibrium, and the net transfer was close to zero for the planet as a whole.

The major changes have occurred following the development of agriculture and industry, with accelerated transfer from the geological (fossil fuels) and terrestrial pools to the atmosphere. Because of the connections between pools, the increased atmospheric carbon concentration affects the oceans and land. The UNFCCC and the Kyoto Protocol represent the first global collaborative attempts by humankind to manage, at least partly, a global element of the Earth System – the carbon cycle. The Kyoto Protocol recognises the role of terrestrial systems as carbon sinks and sources, and it provides a basis for developing future ‘emission trading arrangements’ that involve forests and, potentially, other ecosystems. Understanding of the pathways through which the anthropogenic CO2 is absorbed from the atmosphere and transferred to ecosystems (thus offsetting a portion of the anthropogenic emissions) is fragmentary and incomplete. These factors and dependencies make the quantification and study of the carbon cycle very challenging to model, observe, and predict.

This challenge requires the support of a coordinated set of international activities – scientific research (including modelling), observation and assessment. Assessment is perhaps the most advanced, with the pioneering work of the IPCC providing the scientific assessment required for policy action. In terms of scientific research, the International Geosphere- Biosphere Programme (IGBP) has recently joined forces with the International Human Dimensions Programme on Global Environmental Change (IHDP) and the World Climate Research Programme (WCRP) to build an international framework for integrated research on the carbon cycle (called the Global Carbon Project).

Coordinated observations of the global carbon cycle, including the land, oceans and atmospheric compartments of the cycle, are being promoted within the IGOS Partnership by the Integrated Global Carbon Observations (IGCO) Theme, now operating within the GEO framework.

The IGCO Theme builds on a number of carbon cycle observation initiatives at the Earth’s surface that are underway or planned, including:

— global networks of greenhouse gas measurement stations (such as GLOBALVIEW CO2) and the WMO World Data Centre for Greenhouse Gases (Tokyo);

— global networks of measurement tower sites that monitor the exchanges of CO2, water vapour and energy between terrestrial ecosystems and the atmosphere; e.g. the FLUXNET system has over 260 tower sites operating on a long-term, continuous basis;

— measurement ships and arrays of buoys, including the TAO array in the equatorial Pacific;

— the GEOMON project which aims to sustain and analyse European ground-based observations of atmospheric composition that complement satellite measurements, in order to quantify and understand the ongoing changes. GEOMON is a first step toward building a future integrated pan-European Atmospheric Observing System that will deal with systematic observations of long-lived greenhouse gases, reactive gases, aerosols and stratospheric ozone.

Greenhouse gas cycle.

Data from Earth observation satellites provide the only global, synoptic view of key measures of the carbon cycle, forming an essential part of the envisaged integrated observation strategy planned within IGCO.

The major satellite applications include:

— global mapping of land cover use, land cover change and vegetation cover characteristics that are important to full carbon accounting, using sensors such as AATSR, AVHRR, Landsat TM/ETM/ETM+ and MODIS and carried out through the Global Observation of Forest Cover and Land Cover (GOFC-GOLD) project initiated by CEOS;

— seasonal growth characteristics, including important parameters such as fraction ofAbsorbed Photosynthetically Active Radiation (fAPAR) and Leaf Area Index (LAI), are generated on a global scale (e.g. by AVHRR, MODIS, MERIS, and SPOT VEGETATION sensors);

Flux towers monitor exchanges of CO2, water vapour and energy between land and atmosphere.

— fire detection and burn scar mapping. In many regions of the world, fires are the most significant destroyer of vegetation, driving large inter-annual variations in carbon emissions from ecosystems. Large fires in forests and grasslands are detected and mapped from space, using thermal and optical sensors. (Radar sensors also show promise for burned area mapping);

— helping to map ocean primary productivity as a major sink of carbon dioxide is a key goal. The global annual cycle of phytoplankton bloom is a vital part of the carbon cycle and is measured by satellites indirectly through measurements of ocean colour. These measurements are calibrated using in situ data to give more quantitative assessments, while other colour and pigment measurements add further indications of the ocean ecosystem changes;

Fire detection and mapping

Satellite ocean colour sensors provide important information on the ocean's role in the carbon cycle.

— uncertainty in the land and ocean uptake of carbon and its possible change is of great importance and satellites are set to play a major part in monitoring these changes via CO2 fluxes. The air/land and air/ocean CO2 flux is key but it can only be measured directly at a few research class, in situ measurement locations. Satellites contribute in many ways to estimating these fluxes indirectly. First a great range of satellite data now provide, especially over the ocean, a major input to atmospheric data analysis and reanalysis that gives the best possible description of the atmosphere. This analysis process, especially the reanalysis of delayed mode data, is now including satellite measurements of both column CO2 and vertical profiles of CO2. This work is still in a research phase at centres like The European Centre for Medium-Range Weather Forecasts (ECMWF) and it is expected that, in the future, the regional sources of CO2 will be able to be monitored this way over both land and sea.

Another key role for satellites relates to monitoring of the Kyoto Protocol’s ‘carbon trading’ mechanisms, especially the Clean Development Mechanism (CDM). Existing archives of moderate resolution satellite land imagery (e.g. from Landsat and SPOT) provide the capacity for determining eligibility of CDM reforestation projects by confirming compliance with the Kyoto Protocol’s rule that any proposed forestry project must be able to prove that the site “did not contain forest on 31st December 1989”. The same technologies can also provide geographically explicit land use data for national inventory Satellite ocean colour sensors provide important information on the ocean’s role in the carbon cycle. reports concerning carbon sinks. In addition, they provide important information in trade-offs and conflicts between mitigation/adaptation carbon initiatives involving present land use (including forestry), changes in land use over time, and long-term sustainable development strategies.

Future Challenges

Within the next few years, scientists are hopeful of an extraordinary and unique revolution in global monitoring of atmospheric CO2 concentrations, sources, and sinks, taking advantage of space-based, high-precision measurements of column-integrated CO2 molecular density with global, frequent coverage.

The precision requirements for such measurements are extremely taxing, requiring concentrations as low as 0.3% (1 ppm) to be achieved in order to accurately characterise carbon sources and sinks. A number of new missions, specifically dedicated to this challenge, are being planned to provide the such data. GOSAT (Greenhouse gas Observing Satellite), provided by JAXA, was launched in 2009, and aims to provide information on CO2. After the a launch failure of the Orbiting Carbon Observatory (OCO) in 2009, NASA plans to launch OCO-2 in 2013. This two-year mission is seen as a pathfinder for future, long-term CO2 monitoring missions, using measurements of reflected sunlight in the short-wave infrared to provide global, high-precision measurements of the column-integrated CO2 mixing ratio.

Scientists continue to make advances in the retrieval of CO2 information from atmospheric sounding instruments. Examples are the interpretation of hyperspectral observations by AIRS on NOAA polar orbiting satellites, IASI on EUMETSAT’s MetOp satellite, and data from atmospheric chemistry instruments such as SCIAMACHY on Envisat.

Part of the future challenge will be to support a monitoring system that is suitably accurate, robust and sustained. This would effectively support the implementation process by assisting the national reporting of agreed information related to protocols and of independent, policy neutral, information that ensures that the effectiveness of the measures can be established. It will also support the monitoring of treaties such as the Kyoto Protocol. For Earth observation satellites this will require a move from research to 5 Case Studies operational status to support international policy frameworks.

The necessary coordination of the satellite missions will be undertaken by CEOS. Recognising the importance of continuity of observations of the atmosphere and its composition, CEOS has established an Atmospheric Chemistry Constellation team. Its objective is to collect and deliver data to improve predictive capabilities for coupled changes in the ozone layer, air quality and climate forcing associated with changes in the environment.

Part III of this document summarises the plans of the world’s space agencies for the necessary observations.

Using data from the SCIAMACHY instrument on Envisat, scientists have for the first time detected regionally elevated atmospheric carbon dioxide
Further Information
Global Carbon Cycle (Woods Hole Research Center):
UNFCCC and Kyoto Protocol:
Global Carbon Project:




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