The+carbon+cycle+and+climate+change

Taylor Johnson, Matt Shea

This diagram shows the realation of carbon in the environment and how it cycles. Basically, carbon is the 4th abundant element in the universe and is needed for life on earth to exist. Every living thing on earth needs carbon for either structure, energy or like humans, both. Carbon is a gas but can also be found in solids such as limestone, wood, plastic, diamonds, and graphite. The cycle consists of several storage pools of carbon such as in the atmosphere, in vegetation, in sediments, and all the others writen in the black text in the diagram. Geographicly, the carbon cycle effects the rock Image came from [|www.imagelearning.com]

In 2001 the IPCC concluded that most of the warming observed over the last half of the twentieth century can be attributed to human activities that have increased greenhouse gas concentrations in the atmosphere. They also warned that these changes will continue to drive rapid climate changes for several centuries to come (IPCC, 2001). Chief amongst these greenhouse gases is CO2, whose atmospheric concentrations have been dramatically altered by human perturbations to the global carbon cycle. Over at least the 420 000 years prior to the twentieth century, the atmospheric concentration of CO2 only varied between ~ 80 ppmv (parts per million volume) (during the glaciations when the global temperature was 8 - 9 oC colder than today) and ~ 180 ppmv (during the interglacial periods where the temperature was similar to present values). This range of variation in atmospheric CO2 is remarkably narrow, given that its concentration is determined by a highly dynamic biogeochemical cycle.This suggests that the global carbon cycle was controlled by powerful biological feedback processes to maintain a close balance between net photosynthetic uptake of CO2 by the biosphere and its total respiration-the net source and sink strengths of the biosphere was very close to zero over at least the last 420,000 years.

There is convincing evidence that the biosphere has played a major role in regulating Earth's climate. In particular, recent data shows that although there have been periods during which Earth's temperature changed abruptly without discernable accompanying changes in the atmospheric CO2 concentrations, the converse does not appear in the glacial-interglacial records (Smith et al. 1999). The warming from glacial to interglacial conditions was relatively rapid, while the cooling phase leading to glaciation was initially rapid (possibly suggesting perturbation by an external event), but eventually gradual (indicating strong feedbacks that act to counter the change). These patterns suggest a long-term asymmetry in the global rates of CO2 uptake and release by the biosphere (Falkowski et al. 2000). The terrestrial and ocean ecosystems act as buffers to maintain the global temperature in a habitable range. In contrast to the long-term record, the atmospheric CO2 concentration today is ~ 370 ppmv - nearly 35% higher than at any time in the past 420 000 years - as a result of human perturbations to the global carbon cycle. The concentration is also rising at a rate that is at least ten times and perhaps as much as one hundred times faster than ever before observed (Falkowski //et al//., 2000). Clearly the biosphere's regulation of the global carbon cycle - and hence the climate system - has changed. Although it is straightforward to quantify the direct anthropogenic inputs of CO2 to the atmosphere, a quantitative explanation of the rates of atmospheric increase has proven immensely challenging, precisely because of the strong feedbacks exerted by terrestrial and ocean ecosystems to the changes. Understanding of the biospheric feedback - the response of the world's biota to the perturbations - is needed both to gauge the magnitude of future impacts and to design appropriate mitigation actions.


 * Figure 1: The natural terrestrial carbon cycle**