Earth’s carbon balance

The Basic Principle CO 2 is a “greenhouse” gas – it absorbs infra-red radiation as heat There are other greenhouse gasses, such as CH 4 and NO 2 but CO 2 is the major one 2

How is CO 2 measured? CO 2 absorbs infra red radiation A test gas sample is compared with a reference gas NOAA monitoring System on Mauna Loa System for measuring leaf photosynthesis Infra red gas analyzers

World network

Mauna Loa US SomoaSouth Pole NOAA Stations

Mauna Loa CO 2 Trend and annual cycle International Geophysical Year

Northern hemisphere effect March-May maximum South pole out of phase

Global growth rate in atmospheric CO 2 Influence of economic downturns can be seen

Changes in mean annual global temperature

Sea level rise

Potential effects of sea level rise Estimates of sea level rise range between 20 and 110 cm by 2100

Why climate change effects on oceans may pose a serious threat ‘In what is being described as "a groundbreaking move for local government", politicians in the Florida Keys have recognised that climate change is likely to threaten their reefs and beaches with severe damage.’ Hurricane George hits Key West Why climate change effects on sea level poses a serious threat: Small increases in mean sea level may have large effects during storm conditions, e.g., Florida, Maldives, Bangladesh Possible changes in ocean currents, e.g., the Gulf Stream and its effects on Northern Europe – dramatic not incremental Melting of the West Antarctic ice sheet not included in calculating current estimates of sea level increase (potential ~5m rise).

Two Biological Questions 1. Could the earth’s biological systems accumulate sufficient CO 2 to balance ` emissions? 2. What effects may global change have on the earth’s biological systems?

Summary of the earth’s current carbon balance All figures are in billions of tonnes of carbon, Gt C 1 tonne = 1,000 kilo grams

Anthropogenic release Net uptake by terrestrial vegetation Net uptake by the oceans Gain by the atmosphere+3.3 Net uptake by terrestrial vegetation would have to be increased four-fold to off-set the current rate of increase in atmospheric C Could any impact be made as part of a multiplesolution approach? 1. Could the earth’s biological systems accumulate sufficient CO 2 to balance emissions?

A more detailed look at the global carbon cycle, 1990s

Deforestation contributed between a third an a half of the net gain in the atmosphere. If deforestation were halted then the target for CO 2 capture would be less There is four times as much carbon in the soils and detritus of terrestrial ecosystems as there is in their vegetation There is approximately five times as much carbon in accessible reserves as there is in the atmosphere Carbonate in rocks contains the most C by far of any compartment Net primary production is the difference between the amount of carbon gained by growth of plants minus that lost by respiration and decomposition

Global carbon amounts & net primary production in different biomes First Second tC/ha/yr

Some definitions … Biome: all organisms, as well as the physical environment, in a particular area. Biomes are usually characterized by their plant life. E.g., Tundra, tropical rainforest. Biomass: the weight of living material. SINKS : places where a material, or energy, accumulates SOURCES: places that produce or supply a material or energy

Tropical forests have the highest biome net primary production and the second highest total biomass. They are strong SINKS for carbon – but if disturbed so that their soil C is respired they can be strong SOURCES Although temperate forests have the second highest net primary production they have a small global area and so a low total biome C Note that croplands have a low net primary production. This is because crops usually do not cover the ground for much of the year

Growth of young forests to absorb CO 2 “Kyoto Forests” To balance the net gain of 6 Gt of carbon by the atmosphere through planting young forests, and, assuming an increase in production of 5 t ha -1 over the vegetation replaced, e.g., replacing a crop, requires over 10 9 hectares of young forest, ~14 times the size of Washington State. Balancing the CO 2 input from the US alone would require an area ~3 times Washington State ( ~1.2 times the size of California)

2. What effects may global change have on the earth’s biological systems? A. Direct effect of elevated CO 2 B. Multiple effects of elevated CO 2, elevated temperature, and changed nutrient inputs C. Possible changes on the distribution range of biomes and crops

A.Direct effect of elevated CO 2 Net primary productivity is likely to rise but … Enhancement declines as the period of CO 2 enrichment is extended Naturally CO2 enriched sites Acclimation : a change in physiology that enables a plant to maintain a particular pattern or rate of growth, e.g., reduction in stomatal density CO 2 enrichment experiments

FACE: Free Air Carbon Dioxide Enrichment Brookhaven National Lab Panama CO 2 is released into the air to achieve an elevated concentration Experiments are being conducted with a range of crop and vegetation types Catherine Potvin

B. Multiple effects of elevated CO 2, elevated temperature, and changed nutrient inputs Gain in uptake of carbon may be offset by an enhanced respiration, especially microbial respiration associated with decomposition in the soil and organic litter Anthropogenic nitrogen from automobile exhausts and agriculture may cause an increase in productivity

C. Possible changes on the distribution range of biomes and crops Use of global climate change models to predict climate change, along with known present day environmental conditions of different biomes, leads to prediction of major areas of change in vegetation types and that the geographic range of crops will change

Simulated changes in species distributions Sitka spruce: expansion as coastal region becomes wetter Douglas fir: some contraction and expansion No change Contract Expand Sitka spruce Douglas fir

Simulated changes in species distributions No change Contract Expand Engleman spruceDouglas fir Lodgepole pinePonderosa pine Sitka spruceWestern red cedarWestern hemlock Incense cedar

Information about potential tree species change in the western US can be found at: 1. Substantial changes in tree species distribution are predicted. 3. Similar types and sizes of change have taken place since the end of the last glaciation 2. The changes are individualistic – not the same for all species. 4. Predictions of expansion DO NOT TAKE ACCOUNT of trees dispersal requirements 5. Changes in tree distribution since the last glaciation occurred over ~ 10 thousand years.

A “business as usual” approach to CO 2 emissions will lead to a major increase in atmospheric concentrations, doubling by the end of the next century is quite possible Such a change is bound to have major effects on the earth’s biological and geophysical systems Conclusions

Sections you need to have read Courses that deal with this topic There are many courses and seminars that cover particular aspects of climate change. Two to consider are: ESC 202 Global Changes and Forest Biology ATM S 211 Climate and Climate Change