Explain why many scientists believe that human rather that natural causes may be more to blame for recent climate change

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AS Geography                Rosie Austin

Explain why many scientists believe that human rather that natural causes may be more to blame for recent climate change (15 marks).

Evidence of recent climate change is unambiguous. It is true that throughout history climate change has appeared to be cyclical, which we can see on a geological timescale, dating as far as 400 thousand years before present. This timescale shows that climate has always fluctuated as part of a cycle and in many years there have been some periods that are even warmer than the present. This scale shows higher than average temperatures on a long-term basis. A medium term, historical timescale also supports this as it clearly displays cooler and warmer periods, such as a medieval warm period from 1000-1400, and the ‘little’ ice age between 1400-1800.This trend occurred even before the industrial revolution. On studying a shorter term, more recent timescale however, it is clear that such a rapid increase in such a short period of time is an unprecedented phenomenon. The period from 1950-2000 in the northern hemisphere was the warmest 50 year period for 1,300 years, more notably so as such a rapid increase occurred in such a short space of time, whereas previously this change has taken place over thousands of years. It was during this period that 11 of the world’s hottest years occurred since 1850. Instrumental records also show that near-surface air temperatures rose by 0.74°c between 1900 and 2000. The warming trend has been constant since 1960, and 0.65°c of the 0.74°c rise in temperature occurs from 1950 onwards. This change has been recorded across all continents. This data supports each other in that within the past 50 years, temperatures have risen globally.

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Global warming is a fact, but scientists have come up with many explanations as to why this may be. Some suggest that natural causes are to blame for climate change, proposing ideas such as the Milankovitch Theory. This is the theory that variations in the Earth’s orbit around the sun such as a stretch, tilt or wobble of the axis lead to changes in the amount and distribution of solar radiation received by the Earth from the sun. The fact is that although this theory supports ideas of ice ages and warmer inter-glacials, these cycles occur over tens of thousands ...

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