During July 2013, the Scripps Institution of Oceanography measured an average of 397.23 ppm CO2 concentration at their Mauna Loa, Hawai’i Observatory.
This value is important because 397.23 ppm is the largest CO2 concentration value for any July in recorded history. This year’s July value is 2.90 ppm higher than July 2012′s! Month-to-month differences typically range between 1 and 2 ppm. This year-to-year jump is clearly well outside of that range. This change is in line with other months this year: February’s year-over-year change was +3.37 ppm and May’s change was +3.02 ppm. Of course, the unending trend toward higher concentrations with time, no matter the month or specific year-over-year value, as seen in the graphs below, is more significant.
The yearly maximum monthly value normally occurs during May. This year was no different: the 399.89ppm concentration in May 2013 was the highest value reported this year and, prior to the last five months, in recorded history (neglecting proxy data). I expected May of this year to produce another all-time record value and it clearly did that. May 2013′s value will hold onto first place all-time until February 2014.
Figure 1 – Time series of CO2 concentrations measured at Scripp’s Mauna Loa Observatory in July from 1958 through 2013.
CO2Now.org added the `350s` and `400s` to the past few month’s graphics. I suppose they’re meant to imply concentrations shattered 350 ppm back in the 1980s and are pushing up against 400 ppm now in the 2010s. I’m not sure that they add much value to this graph, but perhaps they make an impact on most people’s perception of milestones within the trend.
How do concentration measurements change in calendar years? The following two graphs demonstrate this.
Figure 2 – Monthly CO2 concentration values (red) from 2009 through 2013 (NOAA). Monthly CO2 concentration values with seasonal cycle removed (black). Note the yearly minimum observation occurred nine months ago and the yearly maximum value occurred two months ago. CO2 concentrations will decrease through October 2013, as they do every year after May.
Figure 3 – 50 year time series of CO2 concentrations at Mauna Loa Observatory (NOAA). The red curve represents the seasonal cycle based on monthly average values. The black curve represents the data with the seasonal cycle removed to show the long-term trend. This graph shows the recent and ongoing increase in CO2 concentrations. Remember that as a greenhouse gas, CO2 increases the radiative forcing of the Earth, which increases the amount of energy in our climate system.
CO2 concentrations are increasing at an increasing rate – not a good trend with respect to minimizing future warming. Natural systems are not equipped to remove CO2 emissions quickly from the atmosphere. Indeed, natural systems will take tens of thousands of years to remove the CO2 we emitted in the course of a couple short centuries. Human systems do not yet exist that remove CO2 from any medium (air or water). They are not likely to exist for some time. So NOAA will extend the right side of the above graphs for years and decades to come.
This month, I will return to some graphs I’ve presented before. Here is a 10,000 year view of CO2 concentrations from ice cores to compare to the recent Mauna Loa observations:
Figure 4 – Historical CO2 concentrations from ice core proxies (blue and green curves) and direct observations made at Mauna Loa, Hawai’i (red curve).
Or we could take a really, really long view:
Figure 5 – Historical record of CO2 concentrations from ice core proxy data, 2008 observed CO2 concentration value, and 2 potential future concentration values resulting from lower and higher emissions scenarios used in the IPCC’s AR4.
Note that this graph includes values from the past 800,000 years, 2008 observed values (8-10ppm less than this year’s average value will be) as well as the projected concentrations for 2100 derived from a lower emissions and higher emissions scenarios used by the 2007 IPCC report. If our current emissions rate continues unabated, it looks like a tripling of average pre-industrial concentrations will be our future reality (278 *3 = 834). This graph also clearly demonstrates how anomalous today’s CO2 concentration values are. It further shows how significant projected emission pathways are when we compare them to the past 800,000 years. It is important to realize that we are currently on the higher emissions pathway (towards 800+ppm).
The rise in CO2 concentrations will slow down, stop, and reverse when we decide it will. It depends primarily on the rate at which we emit CO2 into the atmosphere. We can choose 400 ppm or 450 ppm or almost any other target (realistically, 350 ppm seems out of reach within the next couple hundred years). That choice is dependent on the type of policies we decide to implement. It is our current policy to burn fossil fuels because we think doing so is cheap, although current practices are massively inefficient and done without proper market signals. We will widely deploy clean sources of energy when they are cheap; we control that timing. We will remove CO2 from the atmosphere if we have cheap and effective technologies and mechanisms to do so, which we also control to some degree. These future trends depend on today’s innovation and investment in research, development, and deployment. Today’s carbon markets are not the correct mechanism, as they are aptly demonstrating. But the bottom line remains: We will limit future warming and climate effects when we choose to do so.