Ocean Deoxygenation ‘Call for Action’ Research Questioned
Earle et al (2018) recently urged action to tackle climate change this time because of ocean deoxygenation. According to the global warming theory, ocean deoxygenation is one not obvious but important indirect impacts of climate change on the oceans.
It is expected to occur because of reduced oxygenation through decreased oxygen solubility at higher surface temperature, the increased stratification also affecting ocean circulation, and the consequences of warming on biological processes. However, as correctly pointed out by Shepherd, Brewer, Oschlies & Watson (2017), there are still considerable discrepancies between observations and simulations, and our current understanding of both causes and consequences of reduced oxygen in the ocean are inadequate.
If we look indeed at the measured data, for example the monthly average lower troposphere temperature (LTT) above oceans, Figure 1 the global values, the warming rate is much less than the expected, and it is reducing rather than increasing. The measured LTT is only available since 1979. It is proposed by the University of Alabama at Huntsville, USA, www.nsstc.uah.edu. The warming rate (linear fitting) is everything but dramatic, +0.011 K/year for the globe (90S-90N). The warming rate is everything but uniform and dramatically decreasing moving southwards, from the Northern Polar region (60N-90N) value of +0.027 K/year to the Southern Polar region (90S-60S) where it is negative at -0.004 K/year. Looking at the acceleration (parabolic fitting), this parameter is practically zero, but in case small negative at -1.80·10-5 K/year2 for the globe. Similarly, the sea level rate of rise, that is one much more obvious and important direct impact of climate change on the oceans, is everything but dramatic and not accelerating (Parker & Ollier, 2017a,b).
Therefore, while further research on the indirect impacts of climate change on the ocean deoxygenation is certainly important, it is premature to “call for action” as done by Earle et al (2018) discussing the review work by Breitburg et al. (2018). If our understanding of the causes of reduced oxygen in the ocean are not enough, as insufficient is our knowledge of the consequences reduced oxygen in the ocean, there is indeed a very likely opportunity to embrace the wrong measures.
References
Shepherd, J.G., Brewer, P.G., Oschlies, A. & Watson, A.J., 2017. Ocean ventilation and deoxygenation in a warming world: introduction and overview. Philos Trans A Math Phys Eng Sci. 2017; 375(2102):20170240. doi: 10.1098/rsta.2017.0240.
Parker, A. & Ollier, C.D., (2017a), California sea level rise: evidence based forecasts vs model predictions. Ocean & Coastal Management, 149: 198-209. DOI: 10.1016/j.ocecoaman.2017.07.008
Parker, A. & Ollier, C.D., (2017b), Short-Term Tide Gauge Records from One Location are Inadequate to Infer Global Sea-Level Acceleration, Earth Syst Environ, 1: 17. DOI: 10.1007/s41748-017-0019-5.
Earle, S.A., Wright, D.J., Joye, S., Laffoley, D., Baxter, J., Safina, C., Elkus, P., 2018, Ocean deoxygenation: Time for action, Science, 359(6383):1475-1476. DOI: 10.1126/science.aat0167.
Breitburg, D., Levin, L.A., Oschlies, A., Grégoire, M., Chavez, F.P., Conley, D.J., Garçon, V., Gilbert, D., Gutiérrez, D., Isensee, K. & Jacinto, G.S., 2018. Declining oxygen in the global ocean and coastal waters. Science, 359(6371), p.eaam7240. DOI: 10.1126/science.aam7240
Figure 1 – Monthly average lower troposphere temperature (LTT) above oceans, global values (90S-90N). Data from the University of Alabama at Huntsville, USA, www.nsstc.uah.edu. The warming rate (linear fitting) is everything but dramatic, +0.011 K/year. The acceleration (parabolic fitting) is small negative at -1.80·10-5 K/year2. https://qualityassuranceofclimatestudies.files.wordpress.com/2018/03/image1.jpg?w=1000
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