Climate Change- Past And Present Evidence Flashcards
Atmospheric CO2
Keeling Curve 2015 - atmospheric CO2 concentration has risen
385 MLP ppm from 3021 in 1995
CO2 is well mixed- measurement similar even when measured in different places
Seasonal cycles as CO2 is recycled
CO2 Emissions
Since 1750, approx 550 GtC have been emitted
Ocean absorb 150 GtC
Land (plants) absorb 150 GtC
250 GtC left to increase atmospheric concentration
How to measure previous levels of CO2
Extract icicles from Antarctica
Fossilised leaves- count number and size of stomata (lots of CO2, less stomata)
Shells of organisms on sea floor- examine chemical composition, as it depends on how acidic the ocean is, which depends on CO2 in atmosphere
Is CO2 rise just due to natural cycles?
200,000 years ago- magnitude of CO2 change is similar BUT recent change is much more rapid
800,000 years ago- natural cycles in the CO2 levels, occur about every 100,000 years BUT recent increase takes us outside anything we’ve seen in 800,000 years
In 65 million years, there has been times where the CO2 concentration was the same/higher than it is today (3 million years ago)
Why are CO2 levels changing?
Fossils fuels, land use change (deforestation),
ocean absorbs some emissions
The GreenHouse effect
Greenhouse gases don’t react with solar radiation
Earth absorbs sunlight from the sun
Greenhouse gases absorb long wave radiation, radiation emitted from the earth, re-emitted, warms up atmosphere
General Circulation Models (GMCs)
Used to predict the change in the Earth System as a result of change in the atmosphere
Computer representations
Quite and accurate prediction of surface temp (+-5 degrees at least somewhere in the planet)
Precipitation- 20% error in some places
Sea ice- (if melts, amplified warming as sea ice normally reflects heat) not vert accurate, biases
Average of all independent developed models in best at predicting climate change
Radiative forcing
The measurement of the capacity of a gas or other forcing agent to affect the energy balance, thereby contributing to climate change
RF expresses the change in energy in the atmosphere due to GHG emissions
Used to assess & compare the anthropogenic and natural drivers of climate change
How is our planet responding to forcing
Land surface temperature is increasing
Sea surface temperature is increasing
Sea level rising
Sea ice decreasing
What happens when volcanos erupt?
Produces short-term cooling effects
How does deforestation effect the climate?
Leads to slight cooling, as increases reflection
Anthropogenic forcings
Humans are responsible for climate changes
If you remove the increase of greenhouse gases from models, the predictions would show a decrease in earth’s temp
