Earlier today, the Japanese space agency JAXA launched the first orbiter dedicated strictly to monitoring the worldâ''s greenhouse gas emissions. (This in itself is a rather surprising fact, as much of what we know about the greenhouse effect and global warming comes from direct measurement of gases in the atmosphere.) Ibuki will gather information from 56,000 locations around the world, according to JAXA, using two sensors: an infrared instrument to measure backscattering of solar radiation from the earthâ''s surface, enabling calculation of GHG densities; the other to take readings of clouds and aerosols, which can either reflect or absorb radiation.
Ibuki will not be alone for long. Early this year, the United States plans to launch an Orbiting Carbon Observatory, which will be able to measure CO2 entering and leaving the atmosphere close to ground level, so that the major sources and sinks can be more closely specified. Of course many of these are well known and precisely accounted for: emissions from every sizable power plant and every major cement plant are measured and recorded; in gross terms, the oceans absorb about half the carbon thatâ''s pumped into the atmosphere.
But there are important large-scale phenomena such as forest burning and clearing, or dramatic changes in specific ecosystems (sometimes themselves a result of climate change), that can have important carbon effects. For example, the boreal forests of Canada and Siberia are huge absorbers, but those environments are changing frighteningly fast right now because temperature increases have been so disproportionate close to the Arctic.
The United States already has a CO2 monitor on its Aqua satellite, but that instrument takes measurements only of carbon in the upper atmosphere. OCO is the first U.S. satellite dedicated entirely to carbon monitoring. It joins, with Aqua, the â''A Trainâ'' of U.S. satellites that study environmental processes on a global scale.