Book contents
- Frontmatter
- Dedication
- Contents
- Preface
- 1 Ecosystems and Climate
- Part I The Earth System
- Part II Global Physical Climatology
- Part III Hydrometeorology
- Part IV Biometeorology
- Part V Terrestrial Plant Ecology
- Part VI Terrestrial Forcings and Feedbacks
- 25 Terrestrial Ecosystems and Earth System Models
- 26 Seasonal-to-Interannual Variability
- 27 Biogeophysical Climate–Vegetation Dynamics
- 28 Anthropogenic Land Use and Land-Cover Change
- 29 Carbon Cycle–Climate Feedbacks
- 30 Nitrogen, Chemistry, and Climate
- 31 Aerosols, Chemistry, and Climate
- 32 Urbanization
- 33 Climate Intervention and Geoengineering
- 34 Coevolution of Climate and Life
- Appendix
- Index
- Plate section
- References
29 - Carbon Cycle–Climate Feedbacks
from Part VI - Terrestrial Forcings and Feedbacks
Published online by Cambridge University Press: 05 November 2015
- Frontmatter
- Dedication
- Contents
- Preface
- 1 Ecosystems and Climate
- Part I The Earth System
- Part II Global Physical Climatology
- Part III Hydrometeorology
- Part IV Biometeorology
- Part V Terrestrial Plant Ecology
- Part VI Terrestrial Forcings and Feedbacks
- 25 Terrestrial Ecosystems and Earth System Models
- 26 Seasonal-to-Interannual Variability
- 27 Biogeophysical Climate–Vegetation Dynamics
- 28 Anthropogenic Land Use and Land-Cover Change
- 29 Carbon Cycle–Climate Feedbacks
- 30 Nitrogen, Chemistry, and Climate
- 31 Aerosols, Chemistry, and Climate
- 32 Urbanization
- 33 Climate Intervention and Geoengineering
- 34 Coevolution of Climate and Life
- Appendix
- Index
- Plate section
- References
Summary
Chapter Summary
As shown in previous chapters, numerous climate model experiments demonstrate that vegetation exerts an important feedback on climate through energy and water cycles. In addition to these biogeophysical feedbacks, terrestrial ecosystems are coupled to climate through the carbon cycle. Terrestrial ecosystems absorb a significant portion of the annual emission of CO2 to the atmosphere by human activities. This arises from enhanced photosynthesis as a result of climate change, increasing concentration of CO2 in the atmosphere, or by increasing deposition of nitrogen on land. It is also caused by regrowth of forests following abandonment of farmland. At longer timescales, changes in the biogeography of ecosystems alter carbon storage on land. Climate model simulations show that the terrestrial carbon cycle is a positive climate feedback whereby a warmer climate decreases the capacity of the terrestrial biosphere to storage anthropogenic carbon emissions. The uncertainty in the carbon cycle feedback is of comparable magnitude to the uncertainty arising from physical climate processes and relates in part to plant and microbial physiological responses to temperature and plant demographic processes in response to disturbance and climate change. In addition, nitrogen limits the productivity of many terrestrial ecosystems. This control of the carbon cycle by nitrogen results in prominent carbon–nitrogen interactions including constraints on productivity increases with CO2 enrichment, enhanced productivity with nitrogen deposition, and additional nitrogen mineralization with soil warming.
Glacial–Interglacial Cycles
In the absence of human influences, the concentration of CO2 in the atmosphere is the balance between oceanic and terrestrial processes. Over hundreds of thousands of years, atmospheric CO2 has varied by about 100 ppm during glacial–interglacial cycles (Figure 8.2). Atmospheric CO2 was lower during glacial periods (~180–200 ppm) than during interglacial periods (~270–290 ppm). The causes of this variation are unclear, but likely reflect oceanic processes (Ciais et al. 2013). In particular, the colder glacial ocean held more carbon than during warmer interglacial periods because the solubility of CO2 increases with colder temperature. Changes in ocean circulation also contributed to lower atmospheric CO2, while the lower sea level and increased salinity of the glacial ocean decreased oceanic carbon stocks.
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- Information
- Ecological ClimatologyConcepts and Applications, pp. 563 - 593Publisher: Cambridge University PressPrint publication year: 2015