Introduction

Climate System

Causes of Climate Change

Empirical Study of Climate

Climate Modelling

Palaeoclimatic Change

Contemporary Climate Change

Epilogue
Appendix
References

6.4.3. Nitrous Oxide

Nitrous oxide (N2O) is an important, long-lived greenhouse gas that is emitted predominantly by biological sources in soils and water, and removed in the upper atmosphere via photochemical reactions. Unfortunately, estimates of sources and sinks are not well quantified in global terms.

Tropical soils are probably the single most important source of N2O to the atmosphere (Prather et al., 1995), and intensification of tropical agriculture is likely to increase this (Matson & Vitousek, 1990). The current IPCC (1995) estimate for N2O emissions from tropical soils is 4Mt/a (nitrogen), 75% from wet forests soils and 25% from dry savannahs. Temperate soil sources (including forest soils and grasslands) have been estimated at about 2Mt/a. The Earth's oceans are significant sources of N2O. Emissions may be larger than previously estimated (Law & Owen, 1990), accounting for 3Mt/a.

Anthropogenic sources may account for about 40% of total N2O emissions (5.7Mt/a). These include cultivated soils, biomass burning and industrial sources (e.g. nylon production). Total source emissions (natural and anthropogenic) are currently estimated at 14.7Mt/a (± 3.5Mt/a).

Greenhouse Effect

Enhanced G-Effect

Greenhouse Gases
 -Carbon Dioxide
  ·Sources
  ·Sinks
  ·Carbon Cycle
  ·Concentrations
  ·Equilibrium
 -Methane
  ·Sources
  ·Sinks
  ·Concentrations
 -Nitrous Oxide
  ·Sources
  ·Sinks
  ·Concentrations
 -Halocarbons
  ·Sources
  ·Sinks
  ·Concentrations
 -Ozone
 -Other Gases
 -Lifetimes
 -Summary

Greenhouse Forcing
 -Forcing Factors
 -GWPs
 -ΔF-ΔC
 -1765 to 1990
 -Ozone

Aerosols
 -Sources & Sinks
 -Forcing
  ·Direct
  ·Indirect
 -Total Forcing

Climate Variations
 -Surface Temp.
 -Precipitation
 -Other
  ·Stratosphere
  ·Cryosphere
  ·Atmos. Circulation
  ·Cloudiness

Detection
 -Modelling
 -Attribution
  ·Latitudes.
  ·Stratosphere
  ·Precipitation
  ·Sea Level
  ·Fingerprints
 -When?

Future Climate
 -GCM Simulations
 -Feedbacks
  ·Water Vapour
  ·Clouds
  ·Ice Albedo
  ·G-house Gases
 -21st Century

Impacts
 -Agriculture
 -Forestry
 -Ecosystems
 -Water Resources
 -Oceans/Coasts
 -Human & Health

Responses
 -Stabilising
 -FCCC
 -Kyoto Protocol
 -UK Programme
  ·Energy Demand
  ·Energy Supply
 -Evaluation