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The potential of space‐borne imagery to quantify fossil fuel CO2 emissions The potential of space‐borne imagery to quantify fossil fuel CO2 emissions

Philippe Ciais LSCE, France Philippe Ciais LSCE, France

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The global carbon budget

• Emissions of fossil fuels are estimated from energy use statistics

After Lequéré et al., 2014 Satellite data have not been used in this estimate

The 2 ° C goal of the Paris Agreem ent requires a reversal of the trend of CO2 em issions in the short term , and large and sustained reductions in the long term 3

Are w e losing the anchor of the carbon cycle ? Uncertainty of fossil CO2 em issions has not decreased …

Liu et al.

Liu et al. Nature, 2015

based on new coal carbon content measurements from Chinese mines and coal samples

• This 14% correction of emissions translates into adjusting the global land sink

(residual) by 0.4 GtC yr‐1 (~30%)

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Local scale : tw o em ission m aps for transportation in the London area

European data (Stuttgart University) Regional data from UKNAEI

GgC y‐1 per 1 km grid cell

Source ‐ B. Thiruchittampalam IER, Stuttgart U.

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!

No.1 emitting power plant? (postal address)

So care must be taken...

Critical uncertainties in CO2 inventories

Uncertain em issions from hotspots

Source ‐ Courtesy T. Oda

How m easurem ents of atm ospheric CO2 concentration can be used to support em ission reduction policies ?

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• Atmospheric inverse modeling was already proven to be effective to quantify regional CO2 fluxes at global, continental,

regional scales

The atmosphere is a powerful integrator of surface fluxes Atm ospheric inverse m odeling: from CO2 concentrations to em issions

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Em issions are highly localized – > 2 % of the w orld area contain 9 8 % of em issions

• We do not have a dense sampling of the atmosphere in space and in time to elucidate the spatial details of

fossil CO2 emissions beyond continental scales

New generation of satellites to m onitor global anthropogenic em issions

• Satellites offer an unparalleled global spatial

coverage for monitoring greenhouse gas budgets.

• Existing satellites are focused on natural fluxes, but

imagery and long‐term observations provide the

• pportunity to estimate emissions and their trend.
• Significant investments around the world are

preparing future space missions to measure emissions for supporting climate policies.

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Sam pling strategies to m onitor em issions by atm ospheric m easurem ents Sampling over the main emission areas : cities, large power plants

• Needs very high‐resolution measurements &

transport models

• In situ : requires sampling of all large cities
• Needs a new generation of satellites with

imagery capabilities

• Small sources missed. May not give a complete

picture

• Synoptic structures contain a mix of fossil and

natural CO2

• In situ : may not be captured with a sparse

network

• Needs a new generation of satellites with

imagery capabilities

• Emissions signals are rapidly diluted by

transport

Sampling across continental and synoptic scales : fossil CO2 gradients and proxy tracers

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Proxy tracers of CO2 emissions

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The CO2 m issions planned in the year of the Paris Agreem ent No European mission focused on anthropogenic CO2 emissions

GEOCARB

• Policy relevant need for an observing system to

monitor anthropogenic emissions

• Attributes of space infrastructure ( imagery of

column CO2 concentration )

• Attributes of complementary in‐situ infrastructure
• Operational System components
• Detection of emissions from space
• Modeling requirements for

anthropogenic emissions and natural fluxes

Tow ards a European operational m onitoring system

• f anthropogenic CO2 em issions

2015 2017

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Part of the Copernicus Programme Part of a coordinated international carbon observing system

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Needed attributes of space observations of column CO2 for emission monitoring

 Dense sampling (imagery) : images of CO2 plumes produced by emitting areas  High spatial resolution : capture emission hotspots and avoid clouds, pixel size < 3 km  High accuracy : resolve the small atmospheric gradients, individual precision ≈ 1 ppm  Global coverage

Resolution too low Accuracy too low Sampling too sparse Accuracy moderate Sampling sparse Accuracy good Imager : Sampling dense Accuracy good CO2 and CH4 CO2 and CH4 CO2 OCO‐2 (sounder) Microcarb (sounder)

GOSAT

SCIAMACHY (stopped) CO2

Needed Capabilities

GOSATGOSAT

(sounder)

European mission for monitoring CO2 emissions (imager)

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Measuring CO2 from Space

Retrieve variations in the column averaged CO2 dry air mole fraction, XCO2 over the sunlit hemisphere

• Record spectra of CO2

and O2 absorption in reflected sunlight Validate measurements to ensure XCO2 accuracy of 1 ppm (0.25%)

Initial Surf/Atm State Generate Synthetic Spectrum Instrument Model Difference Spectra Inverse Model New State (inc. XCO2)

XCO2

Flask FTS GOSAT and OCO‐2 Tower Aircraft

What are the capabilities of a constellation of CO2 imagers (LEO) to quantify fossil CO2 emissions ?

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Single Single sa satellit llite S7 S7‐1: 1: 1 da day an anim imatio ion (350 (350 km km)

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• MODIS Terra 1km x 1km MOD35 L2 cloud mask as baseline for the orbit
• MODIS provides (nadir centered) LON, LAT, SAZ, CFC, Time (+60min=11:30)
• Computed from modified time (and LON, LAT): SUZ, AZI, GLI
• All other quantities read from geophys. data bases according to LON, LAT, Time

First step : clum ps of em itting pixels that can create plum es detected from space A Clump : “ a cluster of emitting pixels whose CO2 emissions can be detected from space “

• Principle : adjacent high emitting pixels are grouped together
• The plume of a clump can be detected even if plumes of component pixels may not
• Difficult problem : cannot use simply administrative boundaries (e.g. cities) because of hot‐spots near urban areas and

complex patterns of urban emissions (multiple centers)

Aggregation : the method retained is based on detection thresholds and an inverse distance attraction of pixels emissions

Threshold: 1140 tonC a‐1 Threshold: 515 tonC a‐1

64% of global total 73% of global total

Blue background: Urban area from Natural Earth project database

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19 Clum ps distribution in Northern populated regions

China Europe USA

day 44: 1150 day 44: 1145 day 44: 1155 Green: center not in the window; response ignored Red: center in the window; response computed Orange: center in the window; response computed Observation at:

Black dots: Emission‐weighted center of a clump Dark blue: Track of a time window that is targeted Light blue: Pre‐ and post‐ overpasses

Second step : a global 1 km inversion system 20

“Inversion window” 500 km

Strategy : global coverage of all emitting clumps, Bayesian inversion Preserve high spatial and temporal resolution attributes of emissions Allows imagers LEO and GEO OSSE Simple transport model (Gaussian) 100 billions of plumes forming H Numerically optimized Full OSSE takes ≈ 1 week CPU 100 billions of plumes forming H Numerically optimized Full OSSE takes ≈ 1 week CPU

21 How m any days can w e constrain em issions of a city from space? Three cities in France Number of days with an uncertainty reduction better than:

Paris Marseille Dijon 20%

115 days 150 30

50%

70 105 10

80%

35 10 1

Marseille Dijon Paris

Good Bad

30 MtCO2 8 MtCO2 0.8 MtCO2

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… and more than 100 days

3 clumps

4% of national emission More than 30 days

21 clumps

28% of national emission

You want more than 12 ‘good days’

39 clumps

32% of national emission

More than 50 days

19 clumps

26% of national emission

Num ber of ‘good days’ w ith an uncertainty reduction of at least 5 0 % with one space‐borne imager

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intermediate correlation strong correlation

Up‐scaling to annual emission budgets

Importance of temporal error correlations

intermediate correlation strong correlation

If we know emission from one day, do we know emission from another day? To address this question, systematic tests were performed

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intermediate correlation strong correlation intermediate correlation strong correlation

Up‐scaling to annual emission budgets

Importance of temporal error correlations

Co Constella llatio tion C4: C4: 1 da day an anim imatio ion (35 (350 km km)

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Also test GEO configurations

Can proxy tracers help to constrain fossil fuel CO2 emissions?

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Separation of the fossil fuel CO2 em issions using tracers

Energy sector Transportation sector

Column NOx Column CO

Konovalov et al. 2016 ACPD

Proxy tracers are co‐emitted with fossil fuel CO2 through combustion processes

Energy sector

28 Additional constraints on fossil fuel CO2 emissions of the EU from satellite measurements of NOx and CO

From NOx (OMI) From CO (IASI) Combining NOx and CO

Separation of the fossil fuel CO2 com ponent using tracers

Konovalov et al. 2016 ACPD

Potential of S5, MTG future CO observations Uncertain variations in emission factors

• Not too bad number of days with significant improvement of emissions

estimates at city scale ‐ for medium to big cities, even with one imager

• Scaling to annual budget of cities depends critically on temporal error

correlations of emissions => need socioeconomic data to address this question

• Scaling to national scale proves more complicated, with negative and positive

correlations if national totals are already known rather accurately

• Gaussian transport model assumptions too simple (can be improved by cutting

plume lengths).

29 Conclusions – w ill im agers deliver their prom ises ?

Stabilization of greenhouse gases and im plications for observing system s

2018 2050 2100 100 50 20

Critical Verification Period

Fine Grid, Robust Verification Develop Monitoring System

Percent of 2016 Emissions

Year

Establish Baselines 2023 Initial capability 2030 operational capability 2040 Future enhancements

Nationally determined contributions target year

2030

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Take hom e : New Drivers and Changes of carbon observing system s

The Paris Agreement and its 5‐years cycle of global stock taking is a major stakeholder for work that characterizes:

• Progression towards reaching:
• The National Determined Commitments (better understanding of sub‐decadal and decadal variability of the

carbon cycle)

• Peak anthropogenic emissions
• A balance between anthropogenic emissions by sources and removals by sinks of GHG in the second half of

this century (& sinks? – the 2C target),

• A more robust and transparent reporting across all facets of reporting in the UNFCC
• Regional opportunities and consequences of large‐scale negative emissions (land‐based discussion)
• Overall reliance of natural sinks for climate mitigation
• Carbon‐Climate Feedbacks, Hot Spots, and Tipping Points, Ecosystem Collapse (Governments

request).

• Contributions towards IPCC‐AR6, GEO‐Carbon & GHGs Initiative, WMO‐IG3IS, IPBES, others

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Transformational changes of observing systems to support the Paris Agreement

• Quantify efficiency of natural carbon sinks at regional level ( Neutrality Objective)
• Early warning and detection of positive feedbacks of the carbon cycle to climate warming

(1.5 ‐ 2°C warming objective)

• Transform current observations to monitor the effectiveness of negative emissions in the

coming century ( Neutrality Objective)

• Monitor policy effectiveness (short term implementation)
• Emissions and sinks of non CO2 greenhouse gases
• Independent observations to quantify anthropogenic emissions and emissions changes
• Increased spatial resolution of science based estimates of GHG budgets : support

global stock take and NDCs progress

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Thank you for your attention

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Contact : Philippe.ciais@lsce.ipsl.fr