Depends on what "too late" means.
It's already (almost certainly) too late for the Arctic sea ice.
As for the planet, in general, the IPCC finds -
“A leaked draft of the report sent to governments in December suggests that in order to keep global temperature increases below 2 degrees Celsius (3.6 F) by the end of the century — the stated goal of international climate talks — emissions need to fall by 40-70 percent by 2050.”
http://www.evwind.es/2014/04/05/what-is-the-future-of-fossil-fuel/44609
That's 35 years to drop emissions 40% to 70% from 2005 levels. The US is already down 10% from 2005 in terms of energy related CO2 emissions. I don't see any significant problems in us hitting 70%, cutting a bit less than 2% per year. The 40% minimum should be fairly easy - <1% per year.
In about ten years our new cars will be required to average 54.5 MPG. Right now we're averaging around 25 MPG. And there will now be MPG requirements for large and small trucks for the first time. That should result in a roughly 50% drop in CO2 for personal transportation. And it does not take into account the likelihood of a massive move to EVs.
Airplanes and trains will cut fuel use simply because of economics. Buses are starting to move to electricity. New light rail and subway public transportation will be electric.
I expect most of Europe and China to do as well or better. And I expect most developing countries will mostly move straight to renewable energy and install little fossil fuel generation.
Then consider what we've learned and been able to do in the last 20 years. We've taken wind from being expensive to cheap and solar from being far too expensive to affordable. We are pouring huge amounts of effort into new clean energy technology and efficiency. It's hard to believe that we won't make very significant improvements over the next 20 years, leaving us another 15 to get those technologies in place.