The NOAA said on Thursday that atmospheric concentrations of carbon dioxide have reached 400 ppm, the highest level in at least 3 million years, scientists believe. The Scripps Institution of Oceanography recorded a slightly lower estimate of 399.73.
Environmental experts say the new levels are caused by increased global emissions of carbon dioxide from the burning of fossil fuels. Scientists believe that climate change is the direct consequence of carbon dioxide emissions into the atmosphere. Carbon dioxide (CO2) is a heat-trapping or greenhouse gas. A persistent increase in atmospheric CO2 levels is predicted to lead to increasing temperatures.
Some scientists fear that we might have reached a critical threshold at which emissions cause irreversible climate change for 1,000 years even if they are curtailed.
According to CNN, Jim Butler, a senior scientist at NOAA, said: "Once emitted, it (carbon dioxide) remains for the ocean atmosphere system for thousands of years, warming the planet. It changes climate and is driving ocean acidification all that time."
It is feared that rising temperatures could lead to major disruptions of the ecological system and induce climatic changes which could adversely affect human populations.
According to the NOAA , emissions of carbon dioxide due to human industrial activities have increased the atmospheric concentration of CO2 from around 270 to 280 ppm in the late 1700s to the present level of 400 ppm, unsurpassed in at least 800,000 years as evidence of carbon dioxide trapped in ice cores in Antarctica indicate.
Scripps Institution of Oceanography
Ice core data before 1958
The Washington Post reports that while scientists have direct evidence that the present CO2 levels are unmatched in about l million years, Scripps Institution of Oceanography estimates that the last time CO2 levels reached 400 ppm was about 3 to 5 million years ago during the Pliocene Epoch. Scientists say that global average temperatures were then between 5.4 and 7.2 degrees Fahrenheit (3 to 4 degrees Celsius) higher than they are today and sea levels between 16 and 131 feet (5-40 meters) higher.
According to The Washington Post, NOAA senior scientist Pieter Tans, said: "[The] increase is not a surprise to scientists, the evidence is conclusive that the strong growth of global CO2 emissions from the burning of coal, oil, and natural gas is driving the acceleration."
Climate Central reports global CO2 emissions reached 35.6 billion tonnes in 2012, a 2.6 percent increase compared to 2011.
The pattern of rising C02 levels has been monitored since 1958 at the Mauna Loa Observatory in Hawaii. The Keeling Curve constructed from a daily record of atmospheric carbon dioxide levels shows that on the first day in 1958 when measurement was taken, the atmospheric concentration was 313 ppm.
Increase in CO2, Mauna Loa Observatory, Hawaii
Live Science notes that the annual pattern since 1958 has been an increase in C02 which reaches a maximum in May, drops to a minimum in October. The pattern reflects how plants withdraw carbon dioxide from the atmosphere in summer for growth and release it through decaying leaves in winter.
Last 5 days daily average CO2
Scientists are worried about recent patterns of increasing atmospheric CO2 levels. Scripps Institute of Oceanography notes that plotting the graph across annual maximum-minimum fluctuations shows a recent pattern of increase in CO2 levels of about 2 to 2.5 ppm a year, compared to less than 1 ppm a year in 1950s and 1960s.
According to ABC News, the NOAA says that the present rate of carbon dioxide increase is more than 100 times faster than the increase that occurred when the last ice age ended.
Michael Mann, a climate researcher at Pennsylvania State University, said: "We're on course for more than 450 ppm in a matter of decades if we don't get our fossil fuel emissions under control quite soon."
ABC News asked some climate scientists for their thoughts on the rising atmospheric CO2 levels and the trajectory of the Keeling Curve. Waleed Abdalati, Director, Earth Science and Observation Center, Cooperative Institute for Research in Environmental Sciences, said:
"Four-hundred parts per million. On the face of it, it is just a number, not much different from 375 of a decade ago or the 425 we can expect 10 years from now. The true significance is not in the number itself, but in the fact that this point lies on a disturbing trajectory. One has to ask: On a trajectory to what? This level of CO2 -- much of which has been introduced by human activity -- is solidly outside of the naturally occurring bounds of nearly the last million years, and it is only getting worse. So this nice round number is significant, not for what it is, but for what it says about what will be. There is an opportunity here to give this number another significance, by turning into a milestone in which awareness of the trajectory is recognized and meaningfully addressed. Whether or not this is the case remains to be seen."