CARBON CYCLE

The carbon cycle is the circulation and transformation of carbon back and forth between living things and the environment. Carbon compounds are present in living things like plants and animals and in nonliving things like rocks and soil.

The amount of carbon on the earth and in Earth's atmosphere is fixed, but that fixed amount of carbon is dynamic, always changing into different carbon compounds and moving between living and nonliving things.

Carbon is released to the atmosphere from what are called "carbon sources" and stored in plants, animals, rocks, and water in what are called "carbon sinks."

There are many carbon sources like these;
Plants.
Through photosynthesis plants take carbon dioxide out of the atmosphere and release oxygen.The carbon dioxide is converted into carbon compounds that make up the body of the plant, which are stored in both the parts of the plants like shoots, leaves and roots.

Animals.
Animals eat the plants, breath in the oxygen, and exhale carbon dioxide. The carbon dioxide created by animals is then available for plants to use in photosynthesis. Carbon stored in plants that are not eaten by animals eventually decomposes after the plants die, and is either released into the atmosphere or stored in the soil.

Geologic processes.
Large quantities of carbon can be released to the atmosphere through geologic processes like volcanic eruptions and other natural changes that destabilize carbon sinks. For example, increasing temperatures can cause carbon dioxide to be released from the ocean.

While a portion of the total amount of carbon present on the earth runs through the carbon cycle relatively quickly, another portion of the carbon is caught up in long-lived and stable carbon sinks.

In Earth’s past, the carbon cycle has changed in response to climate change. Variations in Earth’s orbit alter the amount of energy Earth receives from the Sun and leads to a cycle of ice ages and warm periods like Earth’s current climate. Today, changes in the carbon cycle are happening because of people. We perturb the carbon cycle by burning fossil fuels and clearing land. By burning coal, oil, and natural gas, we accelerate the process, releasing vast amounts of carbon (carbon that took millions of years to accumulate) into the atmosphere every year.

Today we can obtain the data of amount of emissions from the World Bank web site. (http://data.worldbank.org/indicator/EN.ATM.CO2E.PC/countries/CN-GB-US-ES?display=graph)

CO2 emissions (kt)

 

CO2 emissions (metric tons per capita)

These graphics show that China is the the largest producer of CO2 and USA is the greatest producer per capita. However, we can observe that the amount of emissions per capita in some counties have steadily declined since 2007, excepting China.

Since the beginning of the Industrial Revolution, when people first started burning fossil fuels, carbon dioxide concentrations in the atmosphere have risen from about 280 parts per million to 387 parts per million.
 
Nowadays human activity has contributed to an atmospheric concentration of carbon dioxide not seen since the Pliocene epoch between 2.6 and 5.3 million years ago.

Sources:
http://www.esrl.noaa.gov/gmd/ccgg/trends/#mlo_full
http://earthobservatory.nasa.gov/Features/CarbonCycle/

PAST CLIMATE CHANGE

When we think about climate change it's easy to wonder what happened in the past. This week we are going to learn more about how our climate has changed over the last 4.5 billion years.

The Earth's climate has changed many times before. There have been times when most of the planet was covered in ice, and there have also been much warmer periods. Over at least the last years, temperatures and carbon dioxide levels in the atmosphere have increased and decreased in a cyclical pattern.

To understand this cyclical pattern the BBC has published a series of documentaries on snowball Earth. Link or Youtube

Snowball Earth describes the coldest climate inmaginable. In the distant past the Earth froze over from pole to pole. 

But, how could it be possible?

We know that our climate is controlled by some feedbacks and cycles, particulary in this case, the ice albedo feedback, the water cycle and the carbon dioxide cycle. 

 

ICE ALBEDO FEEDBACK

These cycles can be summarised in this diagram which explain the process of the snowball Earth theory:

 

Amazingly, the Earth is capable of selfregulating, with a series of mechanisms that work together and surprisingly gases like carbon dioxide played a powerful role in governing global climate.

Further information in these links;
Snowball Earth
http://www.bbc.co.uk/nature/ancient_earth/Snowball_Earth
https://www.youtube.com/watch?v=Dv0e-zGGgjQ 
http://globalwarmingsimplified.weebly.com/ 

BLANKET EARTH

I enjoyed this article from NASA, it explains breafly what are the causes of the current global warming.

NASA’s article A blanket around the Earth

Greenhouse gases act as a thermal blanket for the Earth. Most of them are surrounding us, for example methane is a gas produced by human activities like agriculture, carbon dioxide is associated to industrial activities and burning fossil fuels, nitrous oxide is a gas produced by soil cultivations practices, CFC's are used in industrial applications but the most abundant greenhouse gas is water vapour that has a great impact in the Earth's atmosphere warm but it also acts like a feedback mechanism to the climate which will be explained later.

 

The globalisation is a fact and not only do greenhouse gases cause a harmful effect  but also the human activities contribute to warm the planet. The industrial activities have raised atmospheric dioxide level during the last 250 years.

Finally, It's reasonable to assume that the sun's energy can cause the climate change but several evidences show that since 1750 the amount of energy coming from the sun remained constant and if the activity of the sun causes the warming, then we would expect to see warmer temperatures in all layers of the atmosphere and that is not happening.