Global warming is caused by solar radiation, not by human activity.

One often heard argument against human induced global warming goes as follows:

Global warming is mostly the result of natural influences like variations in the climate system and variations in solar radiation.

Let’s have a look and see whether there’s any truth in this statement.

There are many factors which may contribute to climate change. Scientists agree that most of the variability over the last 1,000 years can probably be explained by cooling due to major volcanic eruptions producing large amounts of aerosols with their accompanying cooling effect, and changes in solar heating causing the climate to warm or cool depending on the variation in solar radiation.

In the 20th century the situation becomes more complicated.
There is some evidence that increased solar heating may have led to some warming early in the 20th century, but direct satellite measurements show no appreciable change in solar heating over the last three decades.

Although it’s true that changes in solar activity do affect global temperatures, research shows that, over the last 50 years, increased greenhouse gas concentrations have a much greater effect than changes in the sun’s energy.

The analysis of ice cores as well as marine organisms clearly shows a relationship between atmospheric carbon dioxide levels and global temperatures:
The higher the concentration of this gas, the warmer the planet.

Solar radiation and not human CO2 emissions are responsible for global warming.

Rise in CO2 concentration since 1850

The argument goes thus:
Yes, carbon dioxide in the air has increased in the last century due to the use of fossil fuels. Yes, global average temperature has increased 0.8 degrees C in the same century. Unfortunately, the temperature increase came first: most of the temperature increase was before 1940, and most of the new carbon dioxide was added after 1960. 

The question here is whether the conclusion that temperature rise came before CO2 emissions is correct.

Mean global temperature deviations

Looking at the graphs to the right we see that CO2 concentration has been steadily increasing since 1850.
We also see a temp rise between 1870 and 1880.
To me this looks as though temperature rose as a result of CO2 emissions.
It can’t be a result of solar radiation because between 1870 and 1880 there’s a decrease in solar radiation.

CO2 continues to rise until 1940 and from 1910 to 1940 there’s another steady increase in temperatures.

Solar Radiantion

CO2 emissions stabilize for while during WWII and just thereafter, but around 1960 they start to rise again, hand in hand with global temperatures.

To me it’s very clear from these graphs that temperature rise comes AFTER an increase in CO2 concentrations and not the other way around as some people pretend.
It also looks as though temperature rise comes in jumps, and I would like to further investigate this.

To me it looks as though solar radiation does indeed play a role:

Between 1860 and 1900 solar radiance decreases.
If global warming was a result of solar radiation one would expect global temperatures to get lower at this time, but this is not the case because CO2 concentrations are still rising and have been ever since 1850. Solar radiation and CO2 concentrations compensate for each other and maintain a stable temperature.

From 1900 to 1910 solar radiation is stable and CO2 emissions are stable from 1885 to 1910. Finally there’s a reaction: global temperature decreases as a result of both solar radiation and CO2 concentration stabilization.

From 1910 to 1940 both solar radiance and CO2 levels rise, hand in hand with global temperatures.

From 1940 to 1950 solar radiation increases, this is mitigated by the fact that CO2 levels are stable so that global temperatures remain stable.

From 1950 to 1960 solar radiance continues to increase. During that period CO2 levels also increase. As a result one would expect temp to increase, but it remains stable for a while. It looks as though there’s a delayed reaction to a rise in CO2 levels.

From 1960 to 1980 solar radiantion decreases while CO2 concentration continues to rise. Since one compensates for the other temperatures remain stable.
From 1980 until today solar radiance seems to stabilize while CO2 emissions continue to rise. Not surprisingly global temperatures also continue to rise.

My conclusion is pretty clear:

Solar radiation does indeed effect our climate.
Under normal circumstances the climate would be more or less stable with slightly warmer and cooler periods due to variations in solar radiance.
It’s the rise in carbon dioxide emissions which is preventing the climate from cooling when solar radiance decreases and which is causing the climate to warm as soon as solar radiance stabilizes. Whenever both solar radiance and CO2 emissions increase together, a big rise in temperature takes place.

Therefore it’s the rise in human emitted CO2, and not solar radiance, which is the cause of global warming.

The global warmers can’t explain why satellites show no temperature change in the past 20 years.

The computer models that predict disaster in a century have been completely wrong for the past 20 years.

These are just two other statements I read of people who still deny that global warming is due to human activity.

These statements are simply not true.

A recent NASA study showed that the average temperature around the world in 2011 made it the ninth-warmest year since 1880.

Researchers at the Goddard Institute for Space Studies in New York said the finding is part of a trend in which nine of the 10 warmest years in the modern meteorological record occurred since 2000.

Sources:
http://www.johnstonsarchive.net/environment/co2analysis.html
http://www.upi.com/Science_News/2012/01/19/NASA-Global-warming-trending-up/UPI-52121327015115/#ixzz1kHo61fqw