Here's their most salient conclusions (emphasis mine)
We cannot afford to delay further action to tackle climate change if the long-term target of limiting the global average temperature increase to 2°C, as analysed in the 450 Scenario, is to be achieved at reasonable cost. In the New Policies Scenario, the world is on a trajectory that results in a level of emissions consistent with a long-term average temperature increase of more than 3.5°C. Without these new policies, we are on an even more dangerous track, for a temperature increase of 6°C or more.
Four-fifths of the total energy-related CO2 emissions permissible by 2035 in the 450 Scenario are already “locked-in” by our existing capital stock (power plants, buildings, factories, etc.). If stringent new action is not forthcoming by 2017, the energy-related infrastructure then in place will generate all the CO2 emissions allowed in the 450 Scenario up to 2035, leaving no room for additional power plants, factories and other infrastructure unless they are zero-carbon, which would be extremely costly. Delaying action is a false economy: for every $1 of investment avoided in the power sector before 2020 an additional $4.3 would need to be spent after 2020 to compensate for the increased emissions.
For a more detail discussion see Skeptical Science, basically the IEA looked at 3 future scenario's:
Business as usual = 6°C warming
New Policies (governments meet all pledges made to date) = 3.5°C warming
450ppm (requires much greater action) = 50% chance of limiting warming to 2°C.
2°C warming is seen at the red line we don't want to cross, therefore it is clear much more world action is required.
Time is of the essence to take action to meet a 450 ppm target because existing polluting infrastructure (power plants, factories etc) is almost at the level that uses up all our "carbon budget". The implication of this is that unless action is taken now then worldwide by 2017 any new infrastructure will need to replace those already existing or be zero carbon, or we blow the budget. This is why some news stories have reported we have "5 years" to act on climate change before it is too late.
This is also why those who claim they support climate action, just not now, are misguided. Such a "strategy" is not only far more expensive in the long run, but runs the risk of beginning too late because the "locked in" polluting infrastructure is already great enough to cause dangerous climate change. The fact is a coal plant will operate/ pollute for 50 years, while new but inefficient buildings built today could be around for even longer.
The good news (from Australia's point of view) is that with the passage of the carbon price, we'll be getting started on action. One of the early effects (and perhaps one that is already being felt) will be that new power generation in Australia probably won't include coal plants and that more efficient buildings, factories and appliances will become the norm.
I'll leave the last word to the IEA:
“If we don’t change direction soon, we’ll end up where we’re heading”