...As of April 20, the level of carbon dioxide in the atmosphere was 401.17 ppm. That figure is based on readings from the Mauna Loa Observatory in Hawaii. The scientists who monitor atmospheric carbon dioxide levels expect that levels will stay above 400 ppm until late June or July.

Tans said that the level of CO2 in the atmosphere is now increasing at a rate that is at least 100 times faster than it has been at any time since record-keeping began. At some point next year or the year after, based on current rates, carbon dioxide levels will rise above 400 ppm and will not be likely to fall below that mark again.

The amount of carbon dioxide that gets naturally absorbed from the atmosphere varies according to the time of year, said Tans. During late spring and early summer in the northern hemisphere, trees and plants take in more carbon dioxide from the atmosphere. But as emissions generated by human activities rise, those cycles can no longer offset them. "We are basically overwhelming natural uptake processes," said Tans.

The late Charles David Keeling, a renowned scientist affiliated with the University of California, San Diego, began keeping daily measurements of atmospheric carbon at Mauna Loa in 1958. The record showing the increasing carbon levels at the observatory is today known as the "Keeling Curve." His son, Ralph Keeling, is now the director of the CO2 program at the Scripps Institution of Oceanography at UC-San Diego and has continued to record those levels since his father's death in 2005.

The younger Keeling says the importance of the 400 ppm figure is largely psychological. While there isn't a substantial difference between the impacts of 395 ppm and 405 ppm, crossing that threshold makes it impossible to ignore that something serious is happening.

"When you focus on the fact that it's moving through thresholds like that, you get an appreciation for how it's actually changing," said Keeling. "It's a wake-up call about how much we've already changed the atmosphere."

"I think people accept the reality that CO2 is rising, but they don't have a grasp of what it means quantitatively," he continued. "I hope people remember this moment so that when the hear the carbon dioxide levels are 420 parts per million in a matter of years, they'll say, 'I remember when it was 400.'"

Based on current trends, 420 ppm probably isn't too far off. Currently, carbon dioxide levels are increasing by about 2 parts per million per year. And few countries have given any indication that they plan to cut emissions in the near future -- at least, not enough to affect the trajectory the planet is on.

"The momentum we're seeing right now, going upwards, I think is going to easily carry us through 450 parts per million," said Keeling. "And then I would say even stabilizing before 500 parts per million is probably not going to be very easy."

Bill McKibben, an author and co-founder of the group 350.org, criticized the U.S. government for not doing more to curb emissions. His group draws its name from 350 parts per million -- the level that some scientists have said is the maximum allowable for maintaining ecosystems and the human systems that depend on them...

On Apr 23, 2014, tommy wrote:
What are the communist dreams?

Rep. Michael Grimm (R-N.Y.) appears to have completely reversed his views on climate change as he fights to be reelected to a district hit hard by Hurricane Sandy.

Grimm tells MSNBC's Chris Hayes that his views have evolved in an excerpt from Showtime's “Years of Living Dangerously” series:

CHRIS HAYES: Last time you and I spoke, you said the jury was still out on climate science. Do you still feel that way?

Michael GRIMM: After speaking with Bob Inglis, it made me do some of my own research, you know, I looked at some of the stuff that he sent over, my staff looked at. But the mass majority of respected scientists say that it’s conclusive, the evidence is clear. So I don't think the jury is out.

CHRIS HAYES: The basic story of -- we’re putting carbon in the atmosphere, the planet’s getting warmer, that’s gonna make the sea levels rise -- like, the basic story of that, you pretty much agree with, right?

Michael GRIMM: Sure, I mean there’s no question that, um, you know, the oceans have risen, right? And the climate change part is, is a real part of it. The problem that we're gonna have right now -- there's no oxygen left in the room in Washington for another big debate, that’s the reality.

Grimm's comments to Hayes come just four years after he said at a candidate debate that "the jury is obviously still out" in response to a question about whether he believed climate change is "real."