What's the situation with climate change? How much have we warmed? What's the trajectory? What are the consequences?

aboodman commented 5 years ago

We are estimated to currently be at +1°C from pre-industrial levels (ipcc summary 2018)
We are estimated to hit 1.5 between 2030 and 2052 on current trajectory (ipcc summary 2018)
We are estimated to hit 4 by end of current century, assuming current commitments are met (ipcc data)
- Some estimates for end of century look a little lower, maybe 3.5
- But some also more dire: "If the currently planned actions are not fully implemented, a warming of 4°C could occur as early as the 2060s. Such a warming level by 2100 would not be the end point: a further warming to levels over 6°C would likely occur over the following centuries.” (worldbank)
If we somehow stopped emitting today, we’d probably still get pretty close to 1.5 (ipcc 2018)
Even holding to 2 requires unprecedented global mobilization
Realistically, 4 seems like the path we are currently on.

Summary of some key impacts from Carbon Brief:

	+1.5°C	+2°C	+4°C
Sea level rise by 2100	40cm	50cm	50-100cm (worldbank)
Coral loss	90%	98%
Freshwater availability in mediterranean	-9%	-17%
Hot days	+16%	+25%
Heavy rainfall	+5%	+7%
Wheat and maize	-12%	-24%
Soy and rice	+12%	+13%
Population exposed to severe drought	+132m (+1.7%)	+195m (+2.6%)
Portion of species losing >50% of range	1-8%	2-18%	21-68%

Note that in all scenarios, sea-level rise is strongly delayed. Even with +1.5, total sea-level rise is projected to be 1.5 meters by 2300.

aboodman commented 5 years ago

Need to do more research on what 4 degrees looks like.

aboodman commented 5 years ago

The numbers on sea-level rise are likely wrong. NOAA puts 50cm at the low-end for RCP 4.5. Don't know how that relates to the temperature. See:

aboodman commented 5 years ago

Should probably just eliminate 1.5 column as it is not going to happen.

aboodman commented 5 years ago

The numbers on sea-level rise are likely wrong. NOAA puts 50cm at the low-end for RCP 4.5. Don't know how that relates to the temperature.

Oh, maybe this is consistent on second-thought, if +4 is really where we'll be on current glide path by EOC. Need to dig more into the NOAA paper.

aboodman / climate