In 1999, climate scientists Michael Mann, Raymond Bradley and Malcolm Hughes
published one of the first studies reconstructing northern hemisphere temperatures over the past 1,000 years. They found that temperatures had been relatively flat, but slightly cooling over the past millennium up until the 20th century, at which point there was a rapid
global
warming. Their temperature reconstruction graph had the shape of a stick and blade, and "the hockey stick" was born.
Ever since, the hockey stick model has been one of the main targets of climate skeptics. After all, if the current global warming is unprecedented in the past 1,000 years, that would signal the need to do something to reverse it. The
scientists involved have been under constant attack, as Mann documented in his book "The Hockey Stick and the Climate Wars."
However, a string of subsequent studies by a number of scientific groups from around the world have all yielded essentially the same result. Most recently,
a paper published in the journal Nature Geoscience this week — co-authored by 78 experts from 60 scientific institutions from around the world — found yet another hockey stick. Their temperature reconstruction shows a slow slide into a future ice age ending abruptly with a sharp rise in temperatures in the 19th and 20th centuries. Recent global surface temperatures are probably the warmest in the past 1,400 years.
These new results will undoubtedly generate much discussion within the scientific community. The recent PAGES study is one of the first to include regional records from across the globe to provide a better picture of how climate change varies between regions, which is perhaps more relevant to societies and the environment. The result is a platform from which to conduct further studies and improve model projections of future climate change.[
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Most significantly, the study shows that the global warming over the past century has already erased the long-term cooling from the preceding 2,000 years. The hockey stick is a reality, and the blade will only get sharper with more warming yet to come from continuing
human greenhouse gas emissions.
http://www.livescience.com/29068-hockey-stick-climate.html
