Forum - Global warming

Currently an article is in development with the title Check:_Effects_of_CO2_emissions_on_nature. It's also a general article, with specific spin-off articles. Here below the current version:

According to popular greenhouse radiation theory, the increased emission of greenhouse gasses, in particular carbon dioxide (CO₂) causes global warming as well as other environmental effects such as reducing the pH ("acidification") of the oceans. Estimations of the warming effect of doubling the atmospheric CO2 concentration vary from ca. 0.5 to 5 °C. A popular so-called consensus estimation is ca. 3 °C equilibrium temperature increase. For the transient temperature increase (while it is happening), current estimations are around 1.5 °C.

We will split up the different aspects and assemble the combined evidence on this page. If the conclusions of sub topics are modified, this page will be adapted as needed.

1. Fact Check: CO2 emissions fingerprint on atmospheric CO2

Outcome: There is a reasonably good match; the current CO₂ level increase is almost certainly driven by man-made CO₂ emissions.

2. Fact Check: CO2 emissions fingerprint on sea rise

Outcome: The average sea rise during the last 150 years does not match atmospheric CO₂ increase. It's unclear how much of recently increased sea rise is due to natural causes, and how much is due to CO₂ emissions.

Reality check of predictions: It's enlightening to compare published predictions with the reality. For example in 2014 the Dutch KNMI gave their outlook (their report p.57) based on IPCC predictions of local sea rise for two different emission scenarios, a high ("business as usual") and a low (strong CO2 reduction) scenario. Hereunder we compare their local sea rise projection for the high CO₂ scenario, as actual emissions in recent years were around that scenario (see for example this figure in the journal Nature).

Updated sea level observations. Average of 6 tide gauge stations along the Dutch coast for the period 1901 – 2018, compared with expected sea rise after 2000 based on CO2 models.

It's now obvious that the foreseen increase of sea rise was hugely overestimated. The recent trend line of measurements is still not or hardly bent upwards.

However, an insignificant increase in the rate of sea rise may be simply a not-yet significant increase. Consequently we can't avoid scrutinizing global temperature increases, despite the great difficulties involved. This is discussed next.

3. Fact Check: CO2 emissions fingerprint on temperatures

Outcome: When accounting for possible effects on Northern hemisphere temperatures, a rather good match can be obtained when about 0.5 °C temperature increase since 1880 is ascribed to CO₂ emissions. Notably in recent years the match is much better with CO₂ than without it. As no other man-made greenhouse gasses were accounted for, here "CO₂" stands for all man-made greenhouse gasses and aerosols.

Extrapolating, we can estimate a 1°C transient temperature increase in the Northern hemisphere from a doubling of greenhouse gasses. This estimation is similar to recent estimates by "moderate", non-alarmist climate scientists.

Comments and criticism on this article and its spin-off articles are very welcome!