Sewall: Where Are We Now?

Question 1

Carbon dioxide levels in the atmosphere…

Answer 1

have been rising due to human land clearing and agriculture for around 8,000 years

• CO2 emissions took off mid 19th century during industrial revolution
• CO2 concentrations were around 280 ppm before I.R. and now are over 400 ppm

Question 2

Rise of CO2 in atmosphere…

Answer 2

is associated with a decrease of Earth’s efficiency at emitting radiation to space and a net increase in earth’s temperature of around 1 deg C

Question 3

Where is this warming visible?

Answer 3

in the heat content of the ocean

Question 4

where does this place earth?

Answer 4

on the RCP 8.5 pathway, which is the most aggressive climate change scenario from the IPCC’s 5th assessment with a total warming of 4 deg C by the end of the century