Comparison of global temperature history with CO2 levels curve shows that in the past, average temperature on the globe increased by 12 degrees Celsius with 100 ppm increase of CO2 (please see the figure). Now moving to modern times, let us note that since 1950s, CO2 concentrations increased from 300 to 400 ppm (that is another 100 ppm increase), but the increase of average temperature from 1950 till now is only 0.6 Celsius. Dear colleagues specializing in climatology, how can we explain the lack of expected temperature increase? Isn't it somewhat contradictory to the suggested climate CO2 sensitivity? Why is there such strong conviction that anthropogenic CO2 is really that important in climate change?
It may be a good idea to provide a link to the original full paper from where you obtained the figure.
It is interesting that the 2018 Nobel Prize in economics (environmental economics) went to William D. Nordhouse who is known for his work on climate change models and green accounting.
Recent article in the World Economic Forum provided a 1977 quote from Nordhouse who wrote that: "In contemplating the future course of economic growth in the West, scientists are divided between one group crying “wolf” and another which denies that species’ existence. One persistent concern has been that man’s economic activities would reach a scale where the global climate would be significantly affected. Unlike many of the wolf cries, this one, in my opinion, should be taken very seriously."
https://www.weforum.org/agenda/2018/12/a-planet-at-risk-requires-multilateral-action?utm_source=Facebook%20Videos&utm_medium=Facebook%20Videos&utm_campaign=Facebook%20Video%20Blogs
Shows that you do not understand the role of CO2:
it is not a linear but logarithm relation between increase in CO2 and temperature increase
Start to study instead of jotting down a paragraph without references, for instance here. Clive Best does not believe in Global Warming (he is a so-called denier)
but he knows that it is a Greenhouse gas and that additional CO2 means increased temperature
A second issue is how the water vapor will respond to the increased temperature
http://clivebest.com/blog/?p=4265
That atmospheric CO2 greatly affects the global temperature has been known for almost 200 years. In the early 1800s, Fourier, a French mathematician, identified that the global temperature was greater than expected and reasoned that the earth’s atmosphere must be retaining some of the solar radiation received. Based on laboratory experiments, he proposed that CO2 and water vapour interfere with the infrared radiating from the earth back into space. This process of trapping heat came to be known as the greenhouse effect. In the later 1800s, Arrhenius, a Swedish chemist and Nobel Laureate, made the first calculations quantifying how the atmosphere’s CO2 content affects the global temperature. From that time, the understanding of the factors influencing global climate has improved and shown how complex the controlling mechanisms are. Global temperatures are not just dependent on atmospheric CO2 concentrations, although they remain a major contributor.
The following link presents atmospheric CO2 content and global temperature data for the last 400,000 years based on analysis of Antarctic ice cores. It may be that the information presented by the author of the original question was drawn from this source.
https://www.geocraft.com/WVFossils/last_400k_yrs.html
The CO2 content and the temperature rise and fall over the period, encompassing temperatures both lower and higher than the present time. Visually the trends of the two parameters appear to be in step but it is concluded that the variation of CO2 lags temperature by 800 years suggesting that temperature changes promote the changes in CO2. But what drives the temperature change?
Prior to the current day, four temperature peaks and troughs were experienced.
· The peaks occurred 410,000, 325,000. 240,000, and 130,000 years ago. The corresponding temperatures (relative to 1880) and CO2 levels are, respectively, +2.2°C and 280 ppmv, +3.3°C and 300 ppmv. +2.2°C and 280 ppmv, and +3.2°C and 285 ppmv.
· Following the peaks, the temperatures fell over 75,000 to 110,000 years the decay path including its own peaks and troughs. The minimums occurred 335,000. 250,000, 140,000, and 20,000 years ago. The corresponding temperatures (relative to 1880) and CO2 levels are, respectively, -8.1°C and 200 ppmv, -7.2°C and 200 ppmv. -8.6°C and 190 ppmv, and -8.1°C and 180 ppmv.
· Although the temperature decays take around 100,000 years following irregular trends, the temperature rises are abrupt taking only 10,000 years.
· Over the 400,000-year record, the average global temperature is approximately -5°C (relative to 1880). Not including the present day, over the last 400,000 years the global temperature has been above the 1880 level for less than 20,000 years.
The most recent temperature rise is different than previous ones. The temperature increase commenced 20,000 years ago at the end of the last ice age and then steadied out after 8,000 years 12,000 years ago. The relative temperature was similar to the reference year 1880, i.e. 0°C and the CO2 content was 260 ppmv. Such extended periods of relatively constant temperature were not seen in the previous 400,000 years, so something changed. Agricultural societies started to emerge 12,000 years ago and although world population was only around 5 million, could this be the first anthropogenic effect on global climate? Readers, please provide answers if you have them.
Despite the constant temperature, by 1880 the CO2 content had increased to 290 ppmv, the level associated with the four peak temperatures discussed earlier. Since 1880 the CO2 content has increased to 410 ppmv and the temperature by 0.8°C (relative to 1880), still well below the peak temperatures discussed earlier (2.2 to 3.3°C). However, following the historic trend, the last peak temperature should have occurred 10,000 years ago and temperatures should now be falling not rising. The current rate of temperature increase is alarming; historically the rise was around 1°C per 1000 years; between 1880 and today the rise is 5.7°C per 1000 years, and; in the last 20 years the rise is 17°C per 1000 years. Something has really changed.
So, the deniers who say that climate change is following historic precedent, are expressing an opinion based on thin air (getting thinner as temperatures increase). The changes are very different to when man was not around. Be afraid, very afraid. Or better still, press for our political leaders to do something about it
In addition to earlier replies, it is also important to comprehend myriad of other radiative forcing (for example clouds, methane, aerosols, …….) that affects the global energy balance and hence the global temperature.
May be due to differential response time and other factors, CO2 and global temperature won’t have a linear relation.