Last week there was much buzz in the media about a new paper that used fossils from sediment and ice cores to reconstruct global temperatures for the last 11,000 years.

Typical of the headlines was this one from the Arizona Daily Star: “Study: Global heat spike unique in past 11,000 yrs.” The fuss was caused by this paper: “A Reconstruction of Regional and Global Temperature for the Past 11,300 Years” by Marcott et al., published in Science.

The paper’s graph causing all the stir is shown below:

The paper’s abstract contains this sentence: “Current global temperatures of the past decade have not yet exceeded peak interglacial values but are warmer than during ~75% of the Holocene temperature history.” That alone gives the lie to the graph and to the Star’s headline.

A critique of the paper may be found at WUWT here.

Essentially Marcott et al. used Michael Mann’s hockey stick trick to co-join two data sets of very different resolutions to come up with the spike, in other words they joined apples and oranges.

That procedure blurs out the Medieval Warm Period of about 1,000 years ago even though that period was as warm or warmer than current temperatures.

In the WUWT critiques, Robert Rhode, of the Berkeley Earth Surface Temperature Study, explains the problem:

“They rely on proxy data that is widely spaced in time (median sampling interval 120 years) and in many cases may also be subject to significant dating uncertainty. These effects will both tend to blur and obscure high frequency variability. They estimate…that only 50% of the variance is preserved at 1,000-year periods. This amount of variance suppression is roughly what you would expect if the underlying annual temperature time series had been smoothed with a 400-year moving average. In essence, their reconstruction appears to tell us about past changes in climate with a resolution of about 400 years. That is more than adequate for gathering insights about millennial scale changes during the last 10,000 years, but it will completely obscure any rapid fluctuations having durations less than a few hundred years…..one should be careful in comparing recent decades to early parts of their reconstruction, as one can easily fall into the trap of comparing a single year or decade to what is essentially an average of centuries….since their methodology suppresses most of the high frequency variability, one needs to be cautious when making comparisons between their reconstruction and relatively rapid events like the global warming of the last century.”

Another point from geologist Dr. Don Easterbrook:

“Eighty percent of the source data sites were marine, so temperatures from 80% of the data set used in this paper record ocean water temperatures, not atmospheric temperatures. Thus, they may reflect temperature changes from ocean upwelling, changes in ocean currents, or any one of a number of ocean variations not related to atmospheric climates. This in itself means that the Marcott et al. temperatures are not a reliable measure of changing atmospheric climate.”

Additional comments from Dr. Judith Curry, Georgia Tech: “There doesn’t seem to be anything really new here in terms of our understanding of the Holocene.  Mike’s Nature trick seems to be now a standard practice in paleo reconstructions.  I personally don’t see how this analysis says anything convincing about climate variability on the time scale of a century.”

Interestingly, buried in the supplementary material to their paper, Marcott et al. showed the results of running their data through a computer program which used different algorithms and assumptions. This exercise produced a quite different graph from the same data:

That graph is not nearly as scary looking as the one touted in the headlines. This just goes to show that the results depend on the assumptions and methods used in the computer program: Garbage in – Garbage out. Of course, that graph would not garner headlines.

 

 

 

 

 

WUWT update post: Marcott et al claim of ‘unprecedented’ warming compared to GISP ice core data.  This update from WUWT graphically shows that the current warmth is not unprecedented as claimed.  The first sentence of Marcott et al. says, “Surface temperature reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time.”  This is clearly false.  Anthony Watts superimposes the Marcott data over an earlier study of Greenland ice core data  to get this graph:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 To put things in perspective, look at the following graph, a temperature reconstruction based on ice core data.  Unlike the Marcott paper, this reconstruction shows that current temperatures are among the coolest of the last 10,000 years.  Notice also the previous periods of rapid warming (red lines on the graph).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

UPDATE: April 2, 2013, Ross McKitrick explains how Marcott purposely changed the dates on proxy core to produce the uptick: http://opinion.financialpost.com/2013/04/01/were-not-screwed/

UPDATE: A simple test shows where Marcott goes wrong see here.  See a good explanation of the deception from Resilient Earth here.

Steve McIntyre deconstructs Marcott:

Marcott Mystery #1

No Uptick in Marcott Thesis

Marcott’s Zonal Reconstructions

How Marcottian Upticks Arise

The Marcott-Shakun Dating Service

Hiding the Decline: MD01-2421

 

See also:

20^th Century temperatures explained as natural recovery from Little Ice Age

More evidence that current warming is not unusual

According to a new paper in Nature Climate Change, the impact to global temperature of burning all 170 billion barrels of proven reserves from Alberta’s oil sands between 2012 and 2062 would be a rise in global temperatures by just 0.02 C to 0.05 C.

A co-author of the paper is Dr. Andrew Weaver, Canada Research Chair in Climate Modeling and Analysis at the University of Victoria, and a lead author with the UN Intergovernmental Panel on Climate Change.

Read the story in the Edmonton Journal here.

See also:

Keystone XL pipeline and the Ogallala aquifer

Gasoline prices oil subsidies and politics

Gasoline Prices and the Obama Energy Policy

The Intergovernmental Panel on Climate Change (IPCC) has released a draft summary of its upcoming report on climate change, and the media are hyping the scary scenarios.  Typical is the headline in the Arizona Daily Star: “Scientists: More weather crises are on their way.”

If you think about it a minute, that headline is  equivalent to this: “Scientists predict sun will rise tomorrow.”  Of course we have had and will continue to have weather extremes.

The headline is all too familiar.  Here is another headline from the New York Times:”Scientists Say Earth’s Warming Could Set Off Wide Disruptions.”  That headline was from September 18, 1995.

In the 1995 article, the IPCC made some predictions, one of which we can now test.  They predicted: “A striking retreat of mountain glaciers around the world, accompanied in the Northern Hemisphere by a shrinking snow cover in winter.”

It so happens that the Rutgers University Global Snow Lab keeps track of snow cover. The graph below shows that rather than a  decrease, snow cover in the Northern Hemisphere has been increasing since 1995:

 

 

 

 

 

 

 

 

 

 

 

 

 

We can also look at extreme high and low temperatures.  The National Climate Data Center has a map and table here, which shows that for each state, most of the extreme high and low temperatures occurred before 1950.  Of the 50 states, 29 had record lows and 35 had record highs prior to 1950.

We can also look at the trends for precipitation, drought, and hurricanes:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The United States Geological Survey studied the relationship between floods and rising carbon dioxide.  The USGS found that for most of the country during the last 100 years, there is no strong statistical evidence for flooding increasing or decreasing with rising carbon dioxide.  In the southwest however, they found that flooding has been decreasing with rising carbon dioxide.

“To capture the public imagination, we have to offer up some scary scenarios, make simplified dramatic statements and little mention of any doubts one might have. Each of us has to decide the right balance between being effective, and being honest.” –Dr. Stephen Schneider

The IPCC has lost all credibility except to the credulous press and those with a vested interest in maintaining the carbon dioxide myth.

See also:

The Assumed Authority

Book Review: The Delinquent Teenager Who Was Mistaken for the World’s Top Climate Expert, an IPCC Exposé