BIOEE1610 Carbon Cycle

• The carbon atom has 4 valence electrons. The electron configuration of carbon makes it tetravalent (it can form 4 bonds).
• This means that carbon can form complex and large molecules.
• Carbon forms organic compounds, which are basis of all known life and form the basis of the majority of known chemicals.

• Closer inspection of the data shows that the increase in temperature (in blue) happens rst and then the carbon dioxide concentration (in red) rises.
• This lag time is partly explained by the fact that, as oceans warm up, they release carbon dioxide, because gases dissolve less well in warm water than in cold water.
• A positive feedback loop leads to further increases in temperatures over time: warmer temperatures → more carbon dioxide → even warmer temperatures → even more carbon dioxide, and so on.

• GHGs have the ability to absorb and radiate infrared radiation (heat). When such gases are present, they keep the atmosphere near Earth’s surface warm by absorbing heat from the warmed surface and re-radiating it in all directions, including back down towards the surface.
• In addition to carbon dioxide and water vapour (most important and abundant), methane and nitrogen oxides also contribute to Earth’s greenhouse effect, but to a lesser extent.
• Short wave radiation can enter the atmosphere, however, GHGs block long wave radiation (infrared) reflected from the Earth’s surface and absorb it. The greenhouse gases can then re-radiate the heat in all directions, the way a radiator does in a cold room.
• Some of this heat will be lost to space, but some of the long-wave radiation will be directed down to the surface, keeping it warm.
• The rest will radiate within the atmosphere, preventing it from getting extremely cold at night when no more sunlight is present. When the Sun rises again in the morning, the surface will heat up and the whole process starts again.

• Its concentration in the atmosphere
• Its ability to absorb long-wave radiation (heat)
• Carbon is more concerning that NO and CH4 that actually have more global warming potential because of its concentration in the atmosphere. (35 percent increase since 1750)

• Water vapor is the most important greenhouse gas.
• However, methane, ozone, nitrous oxide fill in holes in the IR spectrum. These are also the gases that human activity has altered the most.

• Sedimentary Rock
• Oceans
• Fossil Fuels
• Living Organisms
• Atmosphere

• Higher photosynthesis (NPP) in summer leading to lower CO2 (trees lose leaves, get less sunlight).
• More fossil fuels used in winter for heating purposes.

• Population growth + increasing standards of life (increasing CO2 emissions per capita)
• The nation producing the emissions is not the one that drives the demand for those emissions. CO2 per capita doesn’t say much about the lifestyles of the citizens of that country. When we see a decrease of emissions in a country, that can’t necessarily be attributed to a shift to green energy, but rather the outsourcing of carbon emissions. Although we typically attribute carbon emissions to the nation producing it,

• Business as usual: humans continue to add CO2 into the atmosphere at the current rate. (continued exponential)
• Increased emissions: Humans will add more CO2 to the atmosphere. (more rapid exponential)
• Reduced emissions: slows down (plato)
• Global extinction: Humans go extinct and stop emitting CO2 (begins to decrease but doesn’t drop to zero)

• Rapid population growth and associated consumer demand for transportation and industry
• Deforestation of tropical rainforests.
• Methane release due to cattles and rice patties.

• Some particles released in industry diffuse short wave radiation and decrease temperatures.
• Even weather forecasts show a degree of uncertainty.

• 10-50 km above sea level
• Short wave UV radiation breaks down oxygen molecules and O atoms combine with O2 to form O3. Halogens under UV radiation also break down, negatively affecting the ozone formation dynamic equilibrium.

• 0-10 km above sea level
• Tropospheric ozone is a pollutant as a result of pollution by volatile organic compounds, Co2 and CO, SO2 and NO. It is a secondary pollutant which forms in the presence of sunlight. (photochemical smog)

• Damages forests and leaves, photosynthetic ability
• Harms lung tissue
• Damages fabric and rubber materials

• Cycled between warm and cold periods lasting about 100 thousand years.
• Pleistocene epoch
• These changes caused significant changes in the distribution and composition of almost all ecosystems.
• Called Milankovitch cycles: Explains the cycles of cold glacial periods and warm interglacial periods due to the changes in Earth’s orbit and the distribution of solar radiation. Earth’s tilt isn’t enough to explain changes in temperature, the positive feedback cycle of the Albedo effect plays an important role as well. Other factors include changes in ocean currents and volcano eruptions reducing the amount of sunlight reaching the surface of the Earth.

• It has largely shown correlation with the amount of atmospheric CO2.
• At the beginning of glacial times, NPP pulled great amounts of CO2 from the atmosphere. Rising NPP was caused by upwelling of nutrients to the surface of the ocean.
• During interglacial times, ocean NPP was as much as 50% lower, resulting in much higher atmospheric CO2

The last 10,000 years.

• Changes in fossils and chemical isotopes found in sediments and glacial ice.
• Tree growth (tree rings)

• Since the changes in global temperatures are much faster than what would be caused by the Earth’s orbit, we look at solar radiation input when considering the potential for changes in solar energy causing global warming.
• These changes in solar radiation are called solar forcing.
• However, the solar radiation reaching Earth has decreased in the past years, disproving this hypothesis.

In industrialized countries, the vast majority of GHG emissions comes from fossil fuel combustion for electricity and heat production, industry and transportation. However, in many countries, deforestation and agriculture are predominant sources.

• Electricity and heat production
• Land use and agriculture
• Industry
• Transportation
• Fossil fuel retrieval and processing
• Buildings