Global greenhouse gas emissions can be traced to five economic sectors: energy, industry, buildings, transport and AFOLU (agriculture, forestry and other land uses). In this topical review we synthesize the literature to explain recent trends in global and regional emissions in each of these sectors. To contextualise our review, we present estimates of greenhouse gas emissions trends by sector from 1990 to 2018, describing the major sources of emissions growth, stability and decline across ten global regions. Both the literature and data emphasize limited progress towards reducing greenhouse gas emissions. The prominent global pattern is a continuation of underlying drivers with few signs of emerging limits to demand, nor of a deep shift towards the delivery of low and zero carbon services across sectors. We observe a moderate decarbonisation of energy systems in Europe and North America, driven by fuel switching and the increasing penetration of renewables. By contrast, in rapidly industrialising regions, fossil-based energy systems have continuously expanded, only very recently slowing down in their growth. Strong demand for materials, floor area, energy services and travel have driven emissions growth in the industry, buildings and transport sectors, particularly in Eastern Asia, Southern Asia and South-East Asia. An expansion of agriculture into carbon-dense tropical forest areas has driven recent increases in AFOLU emissions in Latin America, South-East Asia and Africa. Identifying, understanding, and tackling the most persistent and climate-damaging trends across sectors is a fundamental concern for research and policy as humanity treads deeper into the Anthropocene.

https://iopscience.iop.org/article/10.1088/1748-9326/abee4e/pdf

A review of trends and drivers of greenhouse gas emissions by sector from 1990 to 2018

Annual European Union greenhouse gas inventory 1990-…2011 and inventory report 2013. Copenhagen : European Evironment Agency, 2013, 1159 p.(Technical report No 8/2013) http://www.eea.europa.eu/publications/european-union-greenhouse-gas-inventory-2013 This report is the annual submission of the greenhouse gas inventory of the European Union to the United Nations Framework Convention on Climate Change and the Kyoto Protocol. It presents greenhouse gas emissions between 1990 and 2011 for EU-27, ...

Annual European Union greenhouse gas inventory 1990-…2011 and inventory report 2013

Abstract. We present the organization, instrumentation, datasets, data interpretation,
modeling, and accomplishments of the multinational global atmospheric
measurement program AGAGE (Advanced Global Atmospheric Gases Experiment).
AGAGE is distinguished by its capability to measure globally, at high
frequency, and at multiple sites all the important species in the Montreal
Protocol and all the important non-carbon-dioxide (non-CO2) gases
assessed by the Intergovernmental Panel on Climate Change (CO2 is
also measured at several sites). The scientific objectives of AGAGE are
important in furthering our understanding of global chemical and climatic
phenomena. They are the following: (1) to accurately measure the temporal and
spatial distributions of anthropogenic gases that contribute the majority of
reactive halogen to the stratosphere and/or are strong infrared absorbers
(chlorocarbons, chlorofluorocarbons – CFCs, bromocarbons,
hydrochlorofluorocarbons – HCFCs, hydrofluorocarbons – HFCs and
polyfluorinated compounds (perfluorocarbons – PFCs), nitrogen trifluoride –
NF3, sulfuryl fluoride – SO2F2, and sulfur hexafluoride –
SF6) and use these measurements to determine the global rates of
their emission and/or destruction (i.e., lifetimes); (2) to accurately
measure the global distributions and temporal behaviors and determine the
sources and sinks of non-CO2 biogenic–anthropogenic gases important
to climate change and/or ozone depletion (methane – CH4, nitrous
oxide – N2O,
carbon monoxide – CO, molecular hydrogen – H2, methyl chloride
– CH3Cl, and methyl bromide – CH3Br); (3) to identify new
long-lived greenhouse and ozone-depleting gases (e.g., SO2F2,
NF3, heavy PFCs (C4F10, C5F12,
C6F14, C7F16, and C8F18) and
hydrofluoroolefins (HFOs; e.g., CH2 = CFCF3) have been
identified in AGAGE), initiate the real-time monitoring of these new gases,
and reconstruct their past histories from AGAGE, air archive, and firn air
measurements; (4) to determine the average concentrations and trends of
tropospheric hydroxyl radicals (OH) from the rates of destruction of
atmospheric trichloroethane (CH3CCl3), HFCs, and HCFCs and estimates
of their emissions; (5) to determine from atmospheric observations and
estimates of their destruction rates the magnitudes and distributions by
region of surface sources and sinks of all measured gases; (6) to provide
accurate data on the global accumulation of many of these trace gases that
are used to test the synoptic-, regional-, and global-scale circulations
predicted by three-dimensional models; and (7) to provide global and regional
measurements of methane, carbon monoxide, and molecular hydrogen and
estimates of hydroxyl levels to test primary atmospheric oxidation pathways
at midlatitudes and the tropics. Network Information and Data Repository:
http://agage.mit.edu/data or
http://cdiac.ess-dive.lbl.gov/ndps/alegage.html
(https://doi.org/10.3334/CDIAC/atg.db1001).


History of Chemically and Radiatively Important Atmospheric Gases from the Advanced Global Atmospheric Gases Experiment (AGAGE)

Despite their extent and socio-ecological importance, a comprehensive biogeographical synthesis of drylands is lacking. Here we synthesize the biogeography of key organisms (vascular and non-vascular vegetation and soil microorganisms), attributes (functional traits, spatial patterns, plant-plant and plant-soil interactions) and processes (productivity and land cover) across global drylands. These areas have a long evolutionary history, are centers of diversification for many plant lineages and include important plant diversity hotspots. This diversity captures a strikingly high portion of the variation in leaf functional diversity observed globally. Part of this functional diversity is associated with the large variation in response and effect traits in the shrubs encroaching dryland grasslands. Aridity and its interplay with the traits of interacting plant species largely shapes biogeographical patterns in plant-plant and plant-soil interactions, and in plant spatial patterns. Aridity also drives the composition of biocrust communities and vegetation productivity, which shows large geographical variation. We finish our review discussing major research gaps, which include: i) studying regular vegetation spatial patterns, ii) establishing large-scale plant and biocrust field surveys assessing individual-level trait measurements, iii) knowing whether plant-plant and plant-soil interactions impacts on biodiversity are predictable and iv) assessing how elevated CO2 modulates future aridity conditions and plant productivity.

Biogeography of global drylands

Agriculture is a significant contributor to anthropogenic global warming, and reducing agricultural emissions – largely methane and nitrous oxide – could play a significant role in climate change mitigation. However, there are important differences between carbon dioxide (CO2) which is a stock pollutant, and methane (CH4) which is predominantly a flow pollutant. These dynamics mean that conventional reporting of aggregated CO2-equivalent emission rates is highly ambiguous, and does not straightforwardly reflect historical or anticipated contributions to global temperature change. As a result, the roles and responsibilities of different sectors emitting different gases are similarly obscured by the common means of communicating emission reduction scenarios using CO2-equivalence. We argue for a shift in how we report agricultural greenhouse gas emissions and think about their mitigation to better reflect the distinct roles of different greenhouse gases. Policy-makers, stakeholders and society at large should also be reminded that the role of agriculture in climate mitigation is a much broader topic than climate science alone can inform, including considerations of economic and technical feasibility, preferences for food supply and land-use, and notions of fairness and justice. A more nuanced perspective on the impacts of different emissions could aid these conversations.

/pdf/agriculture-s-contribution-to-climate-change-and-role-in-18yu455ret.pdf

Agriculture's Contribution to Climate Change and Role in Mitigation Is Distinct From Predominantly Fossil CO2-Emitting Sectors.

Nitrous oxide (N2O), like carbon dioxide, is a long-lived greenhouse gas that accumulates in the atmosphere. Over the past 150 years, increasing atmospheric N2O concentrations have contributed to stratospheric ozone depletion1 and climate change2, with the current rate of increase estimated at 2 per cent per decade. Existing national inventories do not provide a full picture of N2O emissions, owing to their omission of natural sources and limitations in methodology for attributing anthropogenic sources. Here we present a global N2O inventory that incorporates both natural and anthropogenic sources and accounts for the interaction between nitrogen additions and the biochemical processes that control N2O emissions. We use bottom-up (inventory, statistical extrapolation of flux measurements, process-based land and ocean modelling) and top-down (atmospheric inversion) approaches to provide a comprehensive quantification of global N2O sources and sinks resulting from 21 natural and human sectors between 1980 and 2016. Global N2O emissions were 17.0 (minimum-maximum estimates: 12.2-23.5) teragrams of nitrogen per year (bottom-up) and 16.9 (15.9-17.7) teragrams of nitrogen per year (top-down) between 2007 and 2016. Global human-induced emissions, which are dominated by nitrogen additions to croplands, increased by 30% over the past four decades to 7.3 (4.2-11.4) teragrams of nitrogen per year. This increase was mainly responsible for the growth in the atmospheric burden. Our findings point to growing N2O emissions in emerging economies-particularly Brazil, China and India. Analysis of process-based model estimates reveals an emerging N2O-climate feedback resulting from interactions between nitrogen additions and climate change. The recent growth in N2O emissions exceeds some of the highest projected emission scenarios3,4, underscoring the urgency to mitigate N2O emissions.

/pdf/a-comprehensive-quantification-of-global-nitrous-oxide-14ehraazdb.pdf

Hanquin Tian

Papers

A comprehensive quantification of global nitrous oxide sources and sinks