The answer to your question, and only your question, is D.
However, I suspect your premise is that the period of high solar activity is the cause of global warming. That hypothesis completely falls apart when you plot total solar irradiance against temperatures.
Since 1958 the trend in solar activity has been declining but temperatures have risen significantly:
http://en.wikipedia.org/wiki/File:Temp-s...
Further, the variation in TSI is nowhere near enough to induce the recent warming. The variation across an entire sunspot cycle is less than 1‰ from the mean. 1363Wm2/yr of TSI warms the planet by 33°C, one thousandth of this is just 0.033°C. The trend change is about one fifth of this or 0.0066°C per year. Even for this small magnitude of warming/cooling to occur would require a prolonged period of high/low TSI.
http://science1.nasa.gov/media/medialibr...
If we look back through the records we find that periods of prolonged high or low solar activity do indeed correspond to warmer and cooler times in Earth’s history.
http://upload.wikimedia.org/wikipedia/co...
But they need to be put into context. The Little Ice Age came about thanks to 600 years of declining solar activity, during this time the average global temperature fell by 0.5°C, or 0.0008°C per year.
http://en.wikipedia.org/wiki/File:Carbon...
The average global temperature has increased by about 0.8°C in recent years, this is the same level of warming that would require 1,000 years of prolonged high TSI and we’ve had nowhere near that.
Furthermore, if solar variation and the sunspot cycle were the cause of global warming then it follows that the climates must follow the sunspot cycle – they don’t, not even close. A sunspot cycle has ≈5? years of pronounced increasing activity followed by ≈5? years of equally pronounced decreasing activity and not by any stretch of the imagination is this signal reflected in the climates.
Put simply, the variation in the Sun is too small to have any significant impact on our climates over short periods of time, at best it can account for 4% of the observed warming. Over many centuries and millennia the effect is compounded and becomes noticeable. And don’t forget, TSI has been declining these past few decades right at the time of the most pronounced warming.
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ADDED:
The sun is the source of heat energy, greenhouse gases are the means by which that energy is retained. No Sun = no global warming, natural or otherwise. No greenhouse gases = no global warming, natural or otherwise. It really is that simple.
If the Sun radiates more or less energy then the planet warms or cools. If greenhouse gas concentrations increase or decrease then the planet warms or cools. Again, it’s that simple.
The variation in solar output is tiny, it’s less than a thousandth of the mean. The variation in greenhouse gas concentrations is huge, it’s 42% and climbing. The Sun provides 33°C of warming, you seem to be saying that the minute variation in TSI can account for all the recent warming – no way, not even close, it defies common sense; not to mention the laws of physics.
The Sun can cause significant warming or cooling but this process takes centuries or millennia, it always has done. The recent warming is of a magnitude that is way beyond anything the Sun could cause. And, as I’ve already stated, the TSI trend is a downward one and has been for the best part of half a century and this is when the most warming has occurred. TSI and temperatures are going in opposite directions. I can’t see why an intelligent person like yourself has difficulty grasping such a simple concept.
The answer is D which is no surprise since from 1250 AD to 1850 AD we were in a period know as the Little Ice Age and we were well below average. Now that we are more at historical average the man made global warming crowd wants us to think this is unusually hot climate based solely on CO2 even though even the experts in Britain who started this has said that the Earth has stayed constant for roughly 15 years now.
Climate scientists have taken solar activity into account. It's not the main driver of temperatures.
Global warming is real. Now start believing!
Trevor - It seems to me that YOU should have picked answer "e" because that seems to be what you are saying.
No D can't be right because all the skeptical-science zealots tell you the solar activity ended 50yrs ago.
dunno
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Please choose the best answer:
a) between the years 1724 to 1801
b) between the years 1847 to 1926
c) between the years 1872 to 1943
d) between the years 1933 to 2012
e) it doesn’t matter because the Sun doesn’t cause global warming.
Hint: Historical Total Solar Irradiance Graph 1611 to 2012
http://lasp.colorado.edu/lisird/tsi/historical_tsi.html
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