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Reconciling greenhouse gas emissions from measurements and modelling in the land use sector | Bob Rees, Kairsty Topp
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Reconciling greenhouse gas emissions from measurements and modelling in the land use sector | Bob Rees, Kairsty Topp

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  • 1. Reconciling greenhouse gasemissions from measurements andmodelling in the land use sectorBob Rees, Kairsty ToppICARB workshop, 5 February 2013
  • 2. Reporting metrics• UK greenhouse gas emissions reported using internationally agreed protocols (IPCC)• Provide simple rule based accounting system• Underpin C footprinting tools• Unlikely to reflect actual emissions• Unhelpful in guiding mitigation 2
  • 3. IPCC approach to GHG inventory IPCC 2006 3
  • 4. Scottish GHG emissions NAEI 2012 4
  • 5. Inter-annual variation of N2Oemissions 5 Smith and Dobbie 2002
  • 6. Historic datasets 70 60 50 Fr e q ue nc y 40 30 20 10 0 - 0 .0 1 0 .0 0 0 .0 1 0 .0 2 0 .0 3 0 .0 4 0 .0 5 0 .0 6 Emis s io n Fa c t o r ( %) An analysis of 237 individual historic UK observations. Buckingham et al 2012 6
  • 7. Climatic controls of nitrous oxideemissions Scottish summersFlechard et al, Agriculture, Ecosystems and Environment 121 (2007) 135–152 7 7
  • 8. Emissions calculations Annual N2O emission (kg N ha-1)  IPCC default EF assumes N2O emissions from soil are supply-related  But at least some 0 100 200 300 400 arable soil emissions Annual N2O emission (kg N ha-1) N application rate (kg ha-1) must be N-balance- related … because they will occur after the crop has taken up some fertiliser N 0 100 200 300 400 N application rate (kg ha-1) 8 Thorman et al, 2012
  • 9. Inventory comparison with Model Is the NAEI emission inventory overestimating UK N2O emissions? 250 200 150 kt N2O/y 100 50 0 1990 1995 2000 2005 2010 NAME 5th 95th Inventory A. Manning 9
  • 10. DEFRA: improving N2O inventory UKIPCC Tier 1 N2Dynamics Model Specific Tier 3 N Dynamics Model Inventory 1% fn{N 10% type, Soil temp} NDevelopment 2 O EFDeposited NH3 fVolatilisation programme will Emissions Deposition N Type Soil Temperature improve structure and 2.5% fn{Soil 28% 30% type}Internationa fLeached l Reporting refine EFLeachate Emissions Model N Leached Emissions Soil Type N Type Factors via plot fn{N type, 0.8% 1.25% SMC, pH} National N/Manure to field scale EFDirect Reporting Applied measurementsSoil Moisture Content Soil pH GHG platform programme 10
  • 11. Process based modelling Soil Characteristics Crop Parameters Climatic Drivers Farming Practices Crop Growth/ Climate Soil Development Physics Soil C,N Biochemistry Crop Production Trace Gas Emissions Soil C, N Dynamics N leaching 11 DNDC
  • 12. Validation Easter Bush 12 12
  • 13. Daily nitrous oxide fluxes in the arable phase of a rotation 800g N2O-N ha-1 d-1 Fertiliser 600 applications 400 200 0 01-Jan 01-Mar 30-Apr 29-Jun 28-Aug 27-Oct 26-Dec DNDC 9.2 Rees et al, 2008 13
  • 14. Regional modelling• Homogeneous Mapping Spatial Unit DNDC (HMSU) etc. – Soil type – Slope – Land cover – Admin boundaries – agronomic practices and climate are similar 14
  • 15. Conclusions• Current inventory reporting of agricultural GHG emissions provide a crude estimate of actual emissions• Improved reporting will help improve the accuracy of emissions and help to deliver mitigation• Revised emission factors in improved modelling will provide opportunities for the development of farming systems with reduced environmental impact 15 15

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