RealClimate logo


The global CO2 rise: the facts, Exxon and the favorite denial tricks

Filed under: — stefan @ 25 January 2018

The basic facts about the global increase of CO2 in our atmosphere are clear and established beyond reasonable doubt. Nevertheless, I’ve recently seen some of the old myths peddled by “climate skeptics” pop up again. Are the forests responsible for the CO2 increase? Or volcanoes? Or perhaps the oceans?

Let’s start with a brief overview of the most important data and facts about the increase in the carbon dioxide concentration in the atmosphere:

  1. Since the beginning of industrialization, the CO2 concentration has risen from 280 ppm (the value of the previous millennia of the Holocene) to now 405 ppm.
  2. This increase by 45 percent (or 125 ppm) is completely caused by humans.
  3. The CO2 concentration is thus now already higher than it has been for several million years.
  4. The additional 125 ppm CO2 have a heating effect of 2 watts per square meter of earth surface, due to the well-known greenhouse effect – enough to raise the global temperature by around 1°C until the present.

Fig. 1 Perhaps the most important scientific measurement series of the 20th century: the CO2 concentration of the atmosphere, measured on Mauna Loa in Hawaii. Other stations of the global CO2 measurement network show almost exactly the same; the most important regional variation is the greatly subdued seasonal cycle at stations in the southern hemisphere. This seasonal variation is mainly due to the “inhaling and exhaling” of the forests over the year on the land masses of the northern hemisphere. Source (updated daily): Scripps Institution of Oceanography. More »

O Say Can You CO2…

Filed under: — group @ 12 October 2017

Guest Commentary by Scott Denning

The Orbiting Carbon Observatory (OCO-2) was launched in 2014 to make fine-scale measurements of the total column concentration of CO2 in the atmosphere. As luck would have it, the initial couple of years of data from OCO-2 documented a period with the fastest rate of CO2 increase ever measured, more than 3 ppm per year (Jacobson et al, 2016;Wang et al, 2017) during a huge El Niño event that also saw global temperatures spike to record levels.

As part of a series of OCO-2 papers being published this week, a new Science paper by Junjie Liu and colleagues used NASA’s comprehensive Carbon Monitoring System to analyze millions of measurements from OCO-2 and other satellites to map the impact of the 2015-16 El Niño on sources and sinks of CO2, providing insight into the mechanisms controlling carbon-climate feedback.

More »

References

  1. J. Wang, N. Zeng, M. Wang, F. Jiang, H. Wang, and Z. Jiang, "Contrasting terrestrial carbon cycle responses to the two strongest El Niño events: 1997–98 and 2015–16 El Niños", Earth System Dynamics Discussions, pp. 1-32, 2017. http://dx.doi.org/10.5194/esd-2017-46
  2. J. Liu, K.W. Bowman, D.S. Schimel, N.C. Parazoo, Z. Jiang, M. Lee, A.A. Bloom, D. Wunch, C. Frankenberg, Y. Sun, C.W. O’Dell, K.R. Gurney, D. Menemenlis, M. Gierach, D. Crisp, and A. Eldering, "Contrasting carbon cycle responses of the tropical continents to the 2015–2016 El Niño", Science, vol. 358, pp. eaam5690, 2017. http://dx.doi.org/10.1126/science.aam5690

1.5ºC: Geophysically impossible or not?

Filed under: — group @ 4 October 2017

Guest commentary by Ben Sanderson

Millar et al’s recent paper in Nature Geoscience has provoked a lot of lively discussion, with the authors of the original paper releasing a statement to clarify that their paper did not suggest that “action to reduce greenhouse gas emissions is no longer urgent“, rather that 1.5ºC (above the pre-industrial) is not “geophysically impossible”.

The range of post-2014 allowable emissions for a 66% chance of not passing 1.5ºC in Millar et al of 200-240GtC implies that the planet would exceed the threshold after 2030 at current emissions levels, compared with the AR5 analysis which would imply most likely exceedance before 2020. Assuming the Millar numbers are correct changes 1.5ºC from fantasy to merely very difficult.

But is this statement overconfident? Last week’s post on Realclimate raised a couple of issues which imply that both the choice of observational dataset and the chosen pre-industrial baseline period can influence the conclusion of how much warming the Earth has experienced to date. Here, I consider three aspects of the analysis – and assess how they influence the conclusions of the study.
More »

…the Harde they fall.

Filed under: — gavin @ 4 October 2017

Back in February we highlighted an obviously wrong paper by Harde which purported to scrutinize the carbon cycle. Well, thanks to a crowd sourced effort which we helped instigate, a comprehensive scrutiny of those claims has just been published. Lead by Peter Köhler, this included scientists from multiple disciplines working together to clearly report on the mistaken assumptions in the Harde paper.

The comment is excellent, and so should be well regarded, but the fact that it is a comment means that the effort will likely be sorely underappreciated. Part of problem is the long time for the process (almost 8 months) which means that the nonsense is mostly forgotten about by the time the comments are published. We’ve discussed trying to speed up and improve the process by having a specialized journal for comments and replications but really the problem here is the low quality of peer review and editorial supervision that allows these pre-rebunked papers to appear in the first place.

GPC is not the only (nor the worst) culprit for this kind of nonsense – indeed we just noticed a bunch of astrology papers in the International Journal of Heat and Technology (by Nicola Scatetta [natch]). It does seem to demonstrate that truly you can indeed publish anything somewhere.

References

  1. P. Köhler, J. Hauck, C. Völker, D.A. Wolf-Gladrow, M. Butzin, J.B. Halpern, K. Rice, and R.E. Zeebe, "Comment on “ Scrutinizing the carbon cycle and CO 2 residence time in the atmosphere ” by H. Harde", Global and Planetary Change, 2017. http://dx.doi.org/10.1016/j.gloplacha.2017.09.015

Climate Sensitivity Estimates and Corrections

You need to be careful in inferring climate sensitivity from observations.

Two climate sensitivity stories this week – both related to how careful you need to be before you can infer constraints from observational data. (You can brush up on the background and definitions here). Both cases – a “Brief Comment Arising” in Nature (that I led) and a new paper from Proistosescu and Huybers (2017) – examine basic assumptions underlying previously published estimates of climate sensitivity and find them wanting.

More »

References

  1. C. Proistosescu, and P.J. Huybers, "Slow climate mode reconciles historical and model-based estimates of climate sensitivity", Science Advances, vol. 3, pp. e1602821, 2017. http://dx.doi.org/10.1126/sciadv.1602821