While there have been countless attempts at correlating sunspot cycles with such diverse p

While there have been countless attempts at correlating sunspot cycles with

such diverse phenomena as the economy, crop yields, and the weather, there has

been little evidence to support these correlations. The past few decades have

Line seen a renewed interest in the sun-climate relationship with a comprehensive

(5) analysis of many different historical records of solar observation. Late in the

seventeenth century, a period known as the Maunder Minimum, there were

virtually no sunspots observed, indicating a "quiet" period in the sun's activity

coinciding with the height of a time known as the Little Ice Age, a period of

lower temperatures in Europe. Once this evidence had been synthesized, it has

(10) become much clearer that there are indeed robust correlations between the

Earth's temperature and sunspots. Perhaps the most important development in

the solar-climate link came when satellites were developed to measure, in rough

terms, the Total Solar Irradiance (TSI), a factor shown to be directly related to

these "activity" cycles. At the maxima of these cycles, there are more sunspots

(15) (magnetic phenomena that attenuate local irradiance), but new instruments

show that these dark sunspots are more than compensated for by bright areas on

the sun called faculae; therefore, the overall irradiance increases in

correspondence with higher numbers of sunspots.

Unfortunately, identifying this evident increase in minimum values as a

(20) trend provokes concern, as there have been only two minima ever measured in

this way. We must be aware that the warming trend in the surface temperature

goes far beyond the last two decades, and that an extension of the solar record

is necessary to assess whether solar activity and irradiance is indeed increasing

at the minima of the cycles and what the potential effect on the climate may be.

(25) The solar record has been extended by the use of the historical sunspot records

already mentioned and correlations have been drawn between solar irradiance

and the temperature curve since 1610, suggesting a predominant solar influence

in the pre-industrial period. But since 1860 only half the observed warming

could be attributable to the irradiance increase, indicating that some other

(30) influence is becoming more influential in controlling the temperature change:

most likely industrial carbon-dioxide.

Recent studies of global warming have necessitated a more comprehensive

effort to quantify the natural climate variability so that the residual change may

be attributed to the anthropogenic emissions of greenhouse gases. This attempt

(35) at quantification of the many different forces effect on the climate has re-

emphasized the complexity of the climate system and the simultaneous

interaction of many influences. Solar irradiance may indeed account for some of

the temperature increases recorded over the last several decades, but as the

atmospheric CO2 rises, due to the exponential increase in emissions from

(40) industrial sources, the influence of solar variability on the Earth's climate will

most likely decrease, and its relative contribution will be far surpassed by

&n

A．presenting two competing scientific theories for the cause of post-industrial climate change and evaluating the body of evidence behind each one

B．giving a brief overview of some recent scientific developments in solar physics and explaining their possible implications for future research

C．discussing the successes in linking terrestrial phenomena with solar activity and indicating how they may have an impact on preventing further climate change

D．pointing out the success of a certain line of scientific inquiry into the terrestrial effects of solar activity while qualifying its successes with regard to climate change

E．outlining the specific reasons why a long standing problem in solar physics is thought to be soluble at last