is in line with a 3.5 degrees warming scenario over the course of
this century – still excluding albedo and carbon feedbacks. These
numbers come from a new pledge
by Climate Interactive and MIT Sloan School of Management.
is the 860 ppm scenario overly pessimistic?
It extrapolates countries’ Intended Nationally Determined
Contributions (INDCs) which are for the Paris climate summit mostly
focussed on the year 2030 over the rest of the century. Shown below
are scenarios with increased levels of ambition beyond 2025/2030.
(The 50% chance 2 degree pathway requires urgent increase of emission
reductions even before 2025.)
is the 860 ppm scenario overly optimistic?
It firstly assumes that countries develop effective national climate
policies and actually reach their INDC emission goals. This has never
before happened on a global scale. Therefore please also always take
note of ‘business as usual’ – the scenario we are actually
which could lead to 1250 ppm CO2eq. Also both the GHG concentration
scenario and the linked warming (climate sensitivity) exclude
feedbacks, many of which are likely to become significant amplifiers
beyond 1.5/2 degrees warming.
scenarios according to Climate Interactive & MIT based on current
to a different group, Climate Action Tracker, the 2 degrees emissions
gap for 2030 INDCs amounts to some 19Gt CO2eq – as
shown in this graph.