Effects of the Changing Carbon Budget Flashcards
How have carbon levels changed over time?
500m years ago, CO2 levels were 20x greater than today.
200m years ago, CO2 levels were 5x greater than today. It then followed a slow decline since pre-industrial levels.
Effects of the changing carbon budget: ocean acidification introduction.
30% of the CO2 in the atmosphere has diffused into the ocean through direct chemical exchange.
Dissolving carbon dioxide into ocean creates carbonic acid - making the alkaline ocean more acidic.
Eg since 1790, ocean’s pH has decreased by 0.1.
Effects of the changing carbon budget: ocean acidification (effect on coral ecosystems and marine organisms).
Carbonic acid reacts with the carbonate ions in the water to form bicarbonate.
But, the carbonate ions in the water is what animals (eg coral and plankton) use to create their calcium carbonate shells.
With less carbonate available, the animals need to expend more energy to build these shells.
As a result mend up with more fragile and thinner shells.
Effect of the changing carbon budget: coral reefs
Coral reefs provide food and livelihood security for 500m people.
Significant reef loss and the consequent fall in marine biodiversity threatens the survival of food availability through reduced food availability and a reduced capacity of the coastline to buffer the impact of sea level rise including increased storm surges.
Effect of the changing carbon budget: ocean acidification (benefit).
More acidic seawater = the better it dissolves calcium carbonate rocks (chalk, limestone).
Over time the more acidic sea water will dissolve more rock, release more carbonate ions and increase the ocean’s capacity to absorb CO2.
Effects of the changing carbon: ocean warming
Warmer oceans caused by climate change could decrease the amount of phytoplankton as they grow better in cool, nutrient rich waters. As a result, this could limit the ocean’s ability to remove carbon from the atmosphere through the biological carbon pump, as well as lessening the effectiveness of the oceans as a carbon sink.
Ocean warming also kills of the symbolic algae which coral needs in order to grow, leading to bleaching and the eventual deaths of reefs.
Effects of the changing carbon budget: melting sea ice.
In the past 35 years sea ice in the Arctic has decreased by 40%. This decrease is due to a positive feedback system whereby sea ice starts to melt, the ocean is able to absorb more sunlight which amplifies the warming.
Bad because sea ice provides a habitat for algae that only appear in more concentrated forms and with more fat content in the ice. The loss of these ice-bound algae affects marine predators all the way up the food chain.
Furthermore, animals like the polar bear rely on sea ice to get their main food source (seals) can no longer travel upon it.
Effects of the changing carbon budget: ocean salinity.
Caused by higher levels of precipitation and higher temperatures, there’s been a decrease in the salinity in the deep ocean. This is because precipitation leads to higher river runoffs which eventually reach the sea. Also, higher temperatures are causing the melting of the Greenland ice sheet and alpine glaciers will lead to an increase in freshwater reaching the oceans.
These changes have been linked to a slowing down of the large-scale oceanic circulation in the North-East Atlantic. In turn this will have an effect on the climate.
Effects of changing carbon budget: rising sea level.
The glacial retreat led to worldwide rise in sea levels 10,000 years ago due to the melting of landlocked freshwater ice. Studies of landforms have shown that sea levels have been much lower in the past - research even shows that sea levels have been increasing by 3.5mm since the early 90s. Causes of this include:
- THERMAL EXPANSION: when water heats up, it expands. Half of the sea level rise in the past century is thought to be caused by warmer oceans having a greater volume and occupying more space. If the oceans continues to warm up, sea levels will rise by 0.8m - 2m by 2100.
- MELTING OF TERRESTRIAL ICE: in recent times, persistently high temperatures have led to an increased rate of summer melting; and a drop in snowfall in shorter winters. This imbalance results in a significant net gain in water entering the ocean compared to evaporation form the sea. Additionally the ice sheets of Antarctica and Greenland are moving quickly towards the ocean due to an increased volume of water lubricating their bases.
Effect of the changing carbon budget: impact on the atmosphere.
The land and oceans take up most of the extra CO2. But 20% may remain in the atmosphere for many 1000s of years. This is significant because CO2 is the most important gas in controlling the Earth’s atmosphere. Carbon dioxide, methane and halocarbons are greenhouse gases that absorb infrared energy (heat) that’s emitted by Earth, and they then re-emit it. The re-emitted energy is scattered in all directions, but some is returned to Earth where it heats the surface. Without greenhouse gases, Earth would be -180C (frozen and too cold), but with too many greenhouse gases, the temperature would be 400C (like Venus and too hot).
Evidently this proves that the greenhouse effect is good for Earth. However the enhanced greenhouse effect (where the extra CO2 and other greenhouse gases in the atmosphere are causing radiactive forcing) is a problem.
Radiactive forcing is a measure of recent human activities and the concept that energy is constantly flowing into the atmosphere in the form of sunlight that always shines on the Earth’s surface. Some of this sunlight (30%) is reflected back into space into much colder surroundings as infrared energy. If the balance between incoming and outgoing energy is anything other than 0, then there will be some warming (or cooling if said number is negative). Radiactive forcing has increased since 1750 also due to changing albedos because of land use changes. It is however difficult to measure radiactive forcing because of complicating factors including natural changes in solar radiation and the effect of aerosols such as carbon particles from diesel exhausts which lead to warming.
If CO2 levels continue to rise at predicted rates, experts predict that the Earth will become much hotter, possibly hot enough to melt much of the existing ice cover.
What’s radiactive forcing?
Radiactive forcing is a measure of human activities and the concept that energy is constantly flowing into the atmosphere in the form of sunlight that always shines on the Earth’s surface.
Some of this sunlight (30%) is reflected back into space into much colder surroundings as infrared radiation.
If the balance between incoming and outgoing energy is anything other than 0, there will be warming or cooling.
Radiactive forcing has increased since the 1750s since changing albedos in land use.
