Forest carbon removals

Overview This carbon removals layer is part of the forest carbon flux model described in Harris et al. (2021) This paper introduces a geospatial monitoring framework for estimating global forest carbon fluxes which can assist a variety of actors and organizations with tracking greenhouse gas fluxes from forests and in decreasing emissions or increasing removals by forests. Forest carbon removals from the atmosphere (sequestration) by forest sinks represent the cumulative carbon captured (megagrams CO2/ha) by the growth of established and newly regrowing forests during the model period between 2001-2025. Removals include accumulation of carbon in both aboveground and belowground live tree biomass. Following IPCC Tier 1 assumptions for forests remaining forests, removals by dead wood, litter, and soil carbon pools are assumed to be zero. In each pixel, carbon removals are calculated following IPCC Guidelines for national greenhouse gas inventories where forests existed in 2000 or were established between 2000 and 2020 according to Potapov et al. (2022) Atmospheric carbon removed in each pixel is based on maps of forest type (e.g., mangrove, plantation), ecozone (e.g., humid Neotropics), forest age (e.g., primary, old secondary), and number of years of carbon removal. This layer reflects the cumulative removals during the model period (2001-2025) and must be divided by 25 to obtain an annual average during the model duration; removal rates cannot be assigned to individual years of the model. All input layers were resampled to a common resolution of 0.00025 x 0.00025 degrees each to match Hansen et al. (2013). We have made several updates to the model since its original release. For documentation through the current version, please refer to this blog. For a more detailed description of the changes included through the 2023 tree cover loss launch (released spring 2024) and a comparison of the model's fluxes with those from the Global Carbon Budget and national greenhouse gas inventories, please refer to this article. Removals are available for download in two different area units over the model duration: 1) megagrams of CO2 removed/ha, and 2) megagrams of CO2 removed/pixel. The first is appropriate for visualizing (mapping) removals because it represents the density of removals per hectare. The second is appropriate for calculating the removals in an area of interest (AOI) because the values of the pixels in the AOI can be summed to obtain the total removals for that area. The values in the latter were calculated by adjusting the removals per hectare by the size of each pixel, which varies by latitude. When estimating removals occurring over a defined number of years between 2001 and 2025 to compare to emissions, divide total carbon removals by the model duration and then multiply by the number of years in the period of interest. Both datasets only include pixels within forests, as defined in the methods of Harris et al. (2021) and updated with tree cover gain through 2020. Related Open Data Portal layers: Forest Carbon Emissions, Net Forest Carbon Flux Resolution: 30 x 30m Google Earth Engine asset and visualization script Geographic Coverage: Global Frequency of Updates: Annual Date of Content: 2001-2025 Cautions Data are the product of modeling and thus have an inherent degree of error and uncertainty. Users are strongly encouraged to read and fully comprehend the metadata and other available documentation prior to data use. Values are applicable to forest areas only (canopy cover >30 percent and >5 m height or areas with tree cover gain). See Harris et al. (2021) for further information on the forest definition used in the analysis. Carbon removals reflect the total removals over the model period of 2001-2025, not an annual time series from which a trend can be derived. Thus, values must be divided by 25 to calculate average annual removals. Uncertainty is higher in gross removals than emissions, particularly driven by uncertainty in removal factors. Carbon removals reflect a gross estimate, i.e., carbon emissions from previous or subsequent loss of tree cover are not included. Instead, gross carbon emissions are accounted for in the companion forest carbon emissions layer. Removals data contain temporal inconsistencies because tree cover gain represents a cumulative total from 2000-2020, rather than annual gains as estimated through 2025. Forest carbon removals reflect those occurring only within forest ecosystems and do not reflect carbon stock increases in the harvested wood products (HWP) pool. Large jumps in removals along some boundaries are due to the use of ecozone-specific removal factors. The changes in removals occur at ecozone boundaries, where different removal factors are applied on each side. This dataset has been updated since its original publication. See Overview for more information.概述 本碳移除图层属于Harris等人（2021）所提出的森林碳通量模型的组成部分。该论文提出了一套用于估算全球森林碳通量的地理空间监测框架，可助力各类主体与机构追踪森林温室气体通量，并助力降低森林碳排放、提升森林碳移除量。 森林碳汇从大气中移除的碳（即碳封存），指2001-2025年模型周期内，成熟林与新再生林生长所累积捕获的碳量（兆克二氧化碳/公顷，megagrams CO2/ha）。碳移除量包含地上与地下活立木生物量中的碳累积。遵循《政府间气候变化专门委员会（Intergovernmental Panel on Climate Change, IPCC）国家温室气体清单指南》中针对留存森林的Tier 1假设，枯木、凋落物与土壤碳库的碳移除量被设定为零。 在每个像元中，碳移除量依据IPCC国家温室气体清单指南进行计算，其适用的森林范围为2000年已存在的森林，或根据Potapov等人（2022）的研究，于2000-2020年间新建立的森林。每个像元移除的大气碳量，基于森林类型（如红树林、人工林）、生态区（如湿润新热带区）、林龄（如原始林、成熟次生林）以及碳移除时长的地图数据。 本图层反映的是2001-2025年模型周期内的累积碳移除量，需将总数值除以25以得到模型周期内的年均移除量；无法将移除率分配至模型的单个年份。所有输入图层均被重采样至统一的0.00025°×0.00025°分辨率，以匹配Hansen等人（2013）的数据集。 本模型自首次发布以来已进行了多次更新。如需查阅当前版本的相关文档，请访问此博客。如需了解2023年树冠覆盖损失更新（2024年春季发布）的详细变更内容，以及本模型通量与全球碳预算（Global Carbon Budget）及国家温室气体清单的对比分析，请参阅此文章。 碳移除量在模型周期内提供两种面积单位的下载选项：1）兆克二氧化碳/公顷（megagrams CO2/ha）；2）每个像元移除的二氧化碳兆克数（megagrams CO2/pixel）。第一种单位适用于碳移除量的可视化（制图），因其代表每公顷的碳移除密度；第二种单位适用于计算关注区域（Area of Interest, AOI）内的碳移除总量，只需将关注区域内所有像元的数值相加即可得到该区域的总碳移除量。第二种单位的数值通过将单位公顷移除量按每个像元的面积进行换算得到，而像元面积随纬度变化。 若需估算2001-2025年间某一特定时长内的碳移除量以与排放量进行对比，可先将总碳移除量除以模型周期时长，再乘以目标时段的年数。两种数据集仅包含符合Harris等人（2021）研究中森林定义，且通过2020年树冠覆盖增益数据更新后的像元。 相关开放数据门户图层：森林碳排放、森林净碳通量 分辨率：30米×30米，提供谷歌地球引擎（Google Earth Engine, GEE）资源与可视化脚本 地理覆盖范围：全球 更新频率：年度 数据覆盖时段：2001-2025年 注意事项 本数据集为模型模拟产物，因此存在固有的误差与不确定性。强烈建议用户在使用数据前，仔细阅读并充分理解元数据及其他可用文档。 数据仅适用于森林区域（树冠覆盖率>30%且树高>5米，或存在树冠覆盖增益的区域）。如需了解本分析中使用的森林定义的详细信息，请参阅Harris等人（2021）的研究。 碳移除量反映的是2001-2025年模型周期内的总移除量，而非可用于推导趋势的年度时间序列数据。因此，需将总数值除以25以计算年均碳移除量。总碳移除量的不确定性高于碳排放的不确定性，这一差异主要由移除因子的不确定性导致。 碳移除量为总估算值，即未包含先前或后续树冠覆盖损失所产生的碳排放。相关的总碳排放量已在配套的森林碳排放图层中进行核算。本碳移除量数据存在时间不一致性，因为树冠覆盖增益为2000-2020年的累积总量，而非截至2025年估算的年度增益数据。 森林碳移除量仅反映森林生态系统内部的碳移除过程，未包含采伐林产品（Harvested Wood Products, HWP）库中的碳储量增量。部分边界处的碳移除量出现大幅跳变，是因为使用了针对特定生态区的移除因子。碳移除量的变化发生在生态区边界处，边界两侧应用了不同的移除因子。 本数据集自首次发布以来已进行多次更新，详细信息请参阅本概述部分。