Towards the UK community exploitation of new satellite measurements of CO2 from the Greenhouse gases Observing SATellite (GOSAT)

人类在许多方面影响了地球气候的演变，其中最引人注目的是化石燃料的燃烧以及随之而来的二氧化碳和其他温室气体的排放。我们从船载测量中得知，在过去200年里，海洋为很大一部分人为碳提供了一个汇，随后阻止了大气中二氧化碳比观测到的更大的增长。大陆上空的二氧化碳也通过生物圈呼吸释放，并被光合作用吸收。这些大陆生物圈二氧化碳源和汇的大小和时空变化，以及它们如何对气候变化作出反应，目前还没有得到很好的了解。更好地定量了解对生物圈大陆二氧化碳通量的控制，对于减少人类对气候的影响的不确定性至关重要。我们对大陆生物圈通量的了解，大部分是从实地数据推断出来的。这些数据在时间和空间上都很稀少，特别是在热带地区，热带雨林（例如亚马逊雨林）被认为占全球二氧化碳通量的很大一部分。由于这一地区的实地资料稀少，很难作出可靠的通量估计。相比之下，海洋二氧化碳通量通常在100公里范围内变化，因此更容易根据现场数据估计全球通量。现在可以从日本温室气体观测卫星（GOSAT）获得具有区域尺度代表性的二氧化碳卫星观测。这些数据将导致我们目前对碳循环的理解发生重大变化，但使用它们对碳循环社区提出了重大挑战。这些数据并不容易解释，它代表了电磁波谱中近红外部分的二氧化碳吸收测量。每天处理成千上万的观测数据也是一项重大的技术挑战。在之前的工作中，我们开发了一种有效的处理工具，从卫星数据中推断二氧化碳的来源和汇，并使用现实的模拟数据对其进行了测试。在这里，我们建议与日本科学小组合作，用GOSAT卫星的真实数据来评估我们的工具。首先，需要对我们的计算机模拟的大气二氧化碳进行仔细和广泛的地面真实处理，因为它将用于解释GOSAT观测到的二氧化碳分布。与此同时，随着对该仪器在空间中的运行情况的逐渐了解，GOSAT的二氧化碳产品将得到改进。其次，一旦我们对计算机模拟和数据有了信心，我们将使用我们的处理工具来计算从卫星数据推断出的第一批二氧化碳通量图。我们预计，即使是我们的早期结果也将有助于改进缓解战略，减少估计未来气候的不确定性。

Humans have influenced the evolution of Earth's climate in many ways, the most dramatic of which has been the burning of fossil fuels and the subsequent emission of carbon dioxide (CO2) and other greenhouse gases. We know from ship-borne measurements that the ocean has provided a sink for a significant fraction of this anthropogenic carbon over the past 200 years, subsequently preventing a larger-than-observed increase in atmospheric CO2. CO2 over continents is also released by biospheric respiration, and is taken up by photosynthesis. The magnitude and spatial and temporal variability of these continental biospheric sources and sinks of CO2, and how they respond to changes in climate, is not well understood. A better quantitative understanding of the controls on biospheric continental CO2 fluxes is essential to reduce uncertainty of the human contribution to climate. Much of what we understand about continental biospheric fluxes has been inferred from in situ data. These data are sparse in both time and space, particularly over the tropics where rainforests (e.g., the Amazon) are thought to represent a significant fraction of global CO2 fluxes. The sparseness of the in situ data over this region makes it difficult to make reliable flux estimates. In contrast, the ocean CO2 fluxes typically vary over 100s km, making it easier to estimate global fluxes from in situ data. Satellite observations of CO2, representative of regional scales, are now available from the Japanese Greenhouse gases Observing SATellite (GOSAT). These data will lead to a step-change in our current understanding of the carbon cycle, but using them presents significant challenges to the carbon cycle community. The data are not straightforward to interpret, representing a measurement of CO2 absorption in the near-infra red portion of the electromagnetic spectrum. Processing the hundreds of thousands of observations per day also represents a significant technical challenge. In previous work we developed an efficient processing tool to infer CO2 sources and sinks from the satellite data and tested it using realistic simulated data. Here, we propose to assess our tool with real data from the GOSAT satellite, in collaboration with the Japanese science teams. First, careful and extensive ground-truthing of our computer simulation of atmospheric CO2 is required because it will be used to interpret the observed distributions of CO2 from GOSAT. At the same time, with progressively better knowledge of how the instrument is performing in space the GOSAT CO2 product will be improved. Second, once we develop confidence in our computer simulation and the data, we will use our processing tool to calculate some of the first CO2 flux maps inferred from satellite data. We anticipate that even our early results will help to improve mitigation strategies and reduce uncertainty in estimate future climate.