Arguments
Sun & climate: moving in opposite directions
What the science says...
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The sun's energy has decreased since the 1980s but the Earth keeps warming faster than before. |
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Climate Myth...
It's the sun
"Over the past few hundred years, there has been a steady increase in the numbers of sunspots, at the time when the Earth has been getting warmer. The data suggests solar activity is influencing the global climate causing the world to get warmer." (BBC)
Over the last 35 years the sun has shown a cooling trend. However global temperatures continue to increase. If the sun's energy is decreasing while the Earth is warming, then the sun can't be the main control of the temperature.
Figure 1 shows the trend in global temperature compared to changes in the amount of solar energy that hits the Earth. The sun's energy fluctuates on a cycle that's about 11 years long. The energy changes by about 0.1% on each cycle. If the Earth's temperature was controlled mainly by the sun, then it should have cooled between 2000 and 2008.
Figure 1: Annual global temperature change (thin light red) with 11 year moving average of temperature (thick dark red). Temperature from NASA GISS. Annual Total Solar Irradiance (thin light blue) with 11 year moving average of TSI (thick dark blue). TSI from 1880 to 1978 from Krivova et al 2007. TSI from 1979 to 2015 from the World Radiation Center (see their PMOD index page for data updates). Plots of the most recent solar irradiance can be found at the Laboratory for Atmospheric and Space Physics LISIRD site.
The solar fluctuations since 1870 have contributed a maximum of 0.1 °C to temperature changes. In recent times the biggest solar fluctuation happened around 1960. But the fastest global warming started in 1980.
Figure 2 shows how much different factors have contributed recent warming. It compares the contributions from the sun, volcanoes, El Niño and greenhouse gases. The sun adds 0.02 to 0.1 °C. Volcanoes cool the Earth by 0.1-0.2 °C. Natural variability (like El Niño) heats or cools by about 0.1-0.2 °C. Greenhouse gases have heated the climate by over 0.8 °C.
Figure 2 Global surface temperature anomalies from 1870 to 2010, and the natural (solar, volcanic, and internal) and anthropogenic factors that influence them. (a) Global surface temperature record (1870–2010) relative to the average global surface temperature for 1961–1990 (black line). A model of global surface temperature change (a: red line) produced using the sum of the impacts on temperature of natural (b, c, d) and anthropogenic factors (e). (b) Estimated temperature response to solar forcing. (c) Estimated temperature response to volcanic eruptions. (d) Estimated temperature variability due to internal variability, here related to the El Niño-Southern Oscillation. (e) Estimated temperature response to anthropogenic forcing, consisting of a warming component from greenhouse gases, and a cooling component from most aerosols. (IPCC AR5, Chap 5)
Some people try to blame the sun for the current rise in temperatures by cherry picking the data. They only show data from periods when sun and climate data track together. They draw a false conclusion by ignoring the last few decades when the data shows the opposite result.
Basic rebuttal written by Larry M, updated by Sarah
Update July 2015:
Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial
This rebuttal was updated by Kyle Pressler in 2021 to replace broken links. The updates are a result of our call for help published in May 2021.
Last updated on 2 April 2017 by Sarah. View Archives
Some regions will experience cool conditions but a number of countries are experiencing record high temperatures this year. 15,000 Russians died in their record heat wave last month. A few months before that, thousands of Pakistanis and Indians died in record heat waves. When you average out the whole planet, we're currently experiencing record high global temperatures.
"how can you say CO2 drives temperature"
We know this because the increased greenhouse effect due to rising CO2 has been directly observed by satellites and confirmed by surface measurements. In other words, several independent measurements directly observe that CO2 is trapping heat.
"ice core samples from Greenland show the opposite and an 800 year lag for the increase in CO2 for the last 12,000 years"
This is discussed in detail on the "CO2 lags temperature" page. In short, warming causes CO2 rise and rising CO2 causes warming. This is a positive feedback and part of the reason that the planet is able to get out of an ice age.
To answer your question "can you really deny the fact that as sun spot activity increases, so do temperatures?", no, you cannot deny that. As the sun gets brighter (eg - more sunspots), the Earth receives more energy and warms. Conversely, as the sunspot activity falls, this equates to less energy reaching the Earth. Over the last 40 years while global temperatures have been rising, the sun has shown a slight cooling trend. This means the sun cannot be causing recent global warming and in fact, is slightly masking the global warming trend.