The climate is always changing, sometimes very abruptly, so the last thing that mankind should be doing is adding its own forcing actions — like pumping unprecedented amounts of greenhouse gases into the atmosphere. Because you never know — you never know — what will tip the balance and send us hurdling into another abrupt change ... and into another era.
This passage sent Mr. Rewrite hurtling toward his reference books. Sure enough, it's a case of hurdle/hurtle confusion. Mr. Friedman should have used hurtle, which means, among other things, to rush violently.
As a verb, hurdle is positive, meaning to clear barriers, or hurdles. That isn't the case with the scenario Mr. Friedman raises.
Here's a good rundown of hurdle vs. hurtle.