Germany’s University of Siegen issued a press release on a recent study conducted by climate scientists. It turns out that natural oceanic cycles indeed do play a far greater role on sea level fluctuations than first believed.
Hat-tip: Die kalte Sonne.
Therefore, because the factors were not correctly considered in the past, we can immediately conclude that the scary projections made by the IPCC for the 21st century were falsely calculated and are thus likely grotesquely exaggerated.
What follows is the University of Siegen press release, which I’ve translated in English.
University of Siegen study shows: The effects of natural ocean cycles on sea level changes is greater than first believed
Scientists all agree that global mean sea level rose by 14 to 21 cm since 1900. Up to now everyone assumed that the largest part of the rise was connected to man-made climate change. However a new calculation by a team of scientists led by German scientist Dr. Sönke Dangendorf of the Water and Environment Institute (fwu) of the University of Siegen now shows the causal uncertainties are much greater than previously assumed. The effects of natural ocean cycles on sea level is thus greater than first believed.
“The uncertainties on the causes of the observed sea level rise since 1900 published up to now fluctuate between 2 and 3 cm. Earlier about 90% of the sea level rise was attributed to anthropogenic effects, i.e. caused by man. These figures are based on the assumption that naturally caused fluctuations in the ocean last merely a few years, and thus explain only a very small part of the observed rise. The latest results however shows that the natural ocean cycles even can persist over decades or centuries. Therefore we can no longer exclude that natural fluctuations may have contributed up to ±8 cm to the observed sea level rise,” says Dangendorf (photo). The results have been published in renowned journal “Nature Communications”.
In its 5th assessment report in 2014 the IPCC summarized that ocean heating and melting of glaciers explain about 80% of the observed sea level rise since 1900. On the other hand the share by the Greenland and Antarctic ice sheets over the said time period still remains uncertain. What’s clear is that neither ocean warming nor the glacier melting can be traced back 100% to anthropogenic effects. Eduardo Zorita, coauthor and scientist at the Helmholtz Center in Geesthacht, adds: “From earlier studies we know that a considerable share of the glacier contribution over the past centuries results from the Little Ice Age and only 50% are connected to anthropogenic factors. Due to insufficient measurements the man-made share of oceanic warming is known only over the past decades, where it reached about 90 percent of the entire warming. It is in any case improbable that the anthropogenic effect was more than 50 or 60% over the entire 20th century because the greenhouse gas emissions accelerated significantly during this period.
[It needs to be pointed out that man may be blamed for ocean warming only if it is proven that man was responsible for the overall global warming to begin with. This is hotly disputed as there is strong evidence of natural factors behind global warming.]
Tide gauges measuring the water level along the coasts are the main sources of data on past sea level changes. One problem these gauges have, however, is that in addition to the effects of oceanic warming and glacier melt they also measure local wind-induced mass redistributions. It’s a fact that these fluctuations dominate the sea level signal over short timescales. Dr. Alfred Müller, coauthor and professor of mathematics at the University of Siegen, argues: “Wind signals mask all long-term changes – not only those anthropogenic, but also natural ocean cycles. In the past this resulted in almost the entire sea level rise being attributed to anthropogenic effects.”
The scientists selected a new approach with which they analyzed the single components of the measured signal separately. As a result this allowed a more precise description of natural variability. “Using our methodology we reach the conclusion that the minimum anthropogenic part of sea level rise since 1900 is about 45%. This number is smaller than assumed previously, but in any case it agrees better with independent studies on single components (e.g. ocean warming, glacier melt),” Dangendorf summarizes. “Also if the values are less than previously assumed, it is important to point out that a significant part of the rise is attributable to anthropogenic effects,” says Dr. Jürgen Jensen, coauthor and professor of hydromechanics and water engineering at the University of Siegen: “For this reason, and in order to minimize the uncertainties in future projections, it is extremely important that we better understand the individual components as well as the natural and anthropogenic factors.”
Dangendorf, S., Marcos, M., Müller, A., Zorita, E., Riva, R.E.M., Berk, K., Jensen, J. (2015): Detecting anthropogenic footprints in sea level rise, Nature Communications, doi:10.1038/ncomms884
Photo credit: University of Siegen