Researchers say that the speed and extent at which the world is heating up because of global warming is unparalleled as a geological event in the past 2,000 years.

There is no comparison between the scale of warming seen over the last century and the famous historic events like the “Little Ice Age”.

The current rate of warming is much faster than had been estimated earlier, the research states. Many of the arguments used by climate sceptics are no longer valid because of the developments, the scientists said.

A number of key eras have stood out when scientists have surveyed the climatic history of our world over the past centuries. The scientists pointed out the events of the “Roman Warm Period” that lasted from AD 250 to AD 400 when there was a unusually warm weather in throughout Europe as well as the now famous Little Ice Age that started from the 1300s and saw temperatures dropping constantly for centuries.

Earlier scientists have pointed these events out to show that there have been many period in the past when the world has warmed and cooled many times over centuries and that the global warming that has been witnessed since the beginning of the industrial revolution was a part of that pattern of warming and cooling. And hence there is perhaps nothing alarming about it.

However that argument was rejected in three new research papers.

700 proxy records of temperature changes, including tree rings, corals and lake sediments, were used by the scientists to reconstruct the climate conditions that prevailed over the past 2,000 years. The scientists concluded that not one of the past climatic events had taken place globally but were mostly confined to regions. For example, in the 15th Century, the Pacific Ocean saw the strongest effect of the Little Ice Age, said the scientists while it was strongest in Europe in the 17th Century.

Typically not more than half of the globe was affected at any one time by the longer-term peaks or troughs in temperature.

There was significant temperature rises only across about 40% of the Earth’s surface during the “Medieval Warm Period” that happened between AD 950 and AD 1250.

Te but in contrast to those historic events, the current warming has affected a very large p[art of the world.

“We find that the warmest period of the past two millennia occurred during the 20th Century for more than 98% of the globe,” one of the papers states. “This provides strong evidence that anthropogenic (human induced) global warming is not only unparalleled in terms of absolute temperatures but also unprecedented in spatial consistency within the context of the past 2,000 years.”

What the researchers saw is that prior to the modern industrial era, the most significant influence on climate was volcanoes. They found no indication that variations in the Sun’s radiation impacted mean global temperatures.

Natural variability is significantly exceeded by the current period, say the authors.

“We see from the instrumental data and also from our reconstruction that in the recent past the warming rate clearly exceeds the natural warming rates that we calculated – that’s another view to look at the extraordinary nature of the present warming,” said Dr Raphael Neukom, from the University of Bern, Switzerland.

Despite the scientists did not examine whether the current climate change is caused primarily because of human activity, the outcome of their research clearly suggests that is the cause.

“We do not focus on looking at what’s causing the most recent warming as this has been done many times and the evidence is always agreeing that it is the anthropogenic cause,” said Dr Neukom.

“We do not explicitly test this; we can only show that natural causes are not sufficient from our data to actually cause the spatial pattern and the warming rate that we are observing now.”

(Adapted from BBC.com)

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