The GLOBAL global warming signal

Skeptical Science


  • New global temperature series confirm the GISTEMP results using only the HadCRUT3, NCDC and/or UAH data.
  • Once El Nino is taken into account there is no evidence for a slowdown in warming over the period 1996-2010.
  • If the HadCRUT4/HadSST3 ocean temperature corrections are also included then the underlying global warming rate is ≳0.2°C/decade.
  • There remain uncorrected cool biases in the temperature trends.


Global warming involves warming of the whole globe (the clue is in the name), but it does not necessarily affect every part of the globe at the same rate.

Different parts of the globe can experience very different changes under greenhouse warming. As a result, if you want to measure global warming, you have to measure the whole globe, not just a part of it. But of the three main in situ temperature records (GISTEMP, NCDC and HadCRUT), only GISTEMP is near-global in coverage over recent decades, and only by means of allowing each weather station to cover a larger region of the map. The incomplete coverage of the Hadley and NCDC datasets may be seen in Figure 1, along with three global temperature reconstructions.

Figure 1: Coverage maps for various temperature seriesFigure 1: Coverage maps for various temperature series. Colors represent mean change in temperature between the periods 1996-2000 and 2006-2010, from +2C (dark red) to -2C (dark blue). Note that the cylindrical projection exaggerates the polar regions of the map.

In this article I will attempt to redress the balance by presenting 16 new versions of the temperature record (10 of which I consider to be realistic), each of which has global or near-global coverage. Thirteen of these are created by creating a composite of a non-global series (HadCRUT3/4, NCDC or BEST) with a global series (GISTEMP, UAH or the NCEP/NCAR reanalysis). The remaining three series are derived by extrapolating the HadCRUT3/4 and NCDC data.

As with my previous article, these results have not been subject to peer review and should be treated as tentative. However the diversity of methods and consistency of the results are strongly suggestive.

Summary of results

I will start by summarizing the results, and then describe the methods and data in detail.

Since the main impact of incomplete coverage is seen in recent temperature trends, we will start by looking at these. The trend over the 15 year period 1996-2010 is shown in Figure 2 for each of the 16 new temperature series (colored bars), compared to the official versions (white bars with coverage percentages superposed). Some of the temperature series have known problems, however two clusters of likely trends have been identified; I have named these the GISS cluster (due to similarity with GISTEMP) and the Had4 cluster (for series based on HadCRUT4).

Figure 1: Global temperature trends 1996-2010Figure 2: Global temperature trends 1996-2010

The global temperature records from these two clusters are shown in Figure 3, along with GISTEMP, NCDC and HadCRUT3 using a 60 month moving average. Use the buttons below the graph to select between 30- and 60- year views. The records are also available as a .CSV file which may be read into any spreadsheet program.

Figure 2: Comparison of official and global temperature series

Figure 2: Comparison of official and global temperature series

Figure 3: Comparison of temperature series (X) 1950-2010 ( ) 1980-2010

The 15 year trend (1996-2010) for the GISS cluster of 6 temperature series is 0.147°C/decade (this is the value for NCDCext, chosen because it is unaffected by the HadSST2 1998 discontinuity). However there has been a tendency towards more frequent La Nina conditions over the period, which has impacted this trend. Foster and Rahmstorf (2011) estimate this influence at -0.026°C/decade, so the underlying warming trend is 0.173°C/decade. This is comparable to the 0.17°C/decade long term trend found by Foster and Rahmstorf. (They also estimate a net cooling effect due to the solar and volcanic influences, however these terms are less well determined and so I have omitted them.)

The 15 year trend (1996-2010) for the Had4 cluster of 3 temperature series, each of which includes the new HadSST3 bias corrections, is 0.179°C/decade (for HAD4ext). Including the El Nino term, the underlying warming trend is 0.205°C/decade.

The two representative trends quoted above are conservative estimates and include a known cool bias due to smoothing – the other trends variously include known cool and warm biases. There is additional evidence for each of these biases, but they have not yet been quantified.


Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


A planet that doesn’t burn, a future that doesn’t suck

My Planet Earth

Creating a Healthy Planet

Planet Earth Weekly

Climate Change and Renewable Energy: Saving Our Planet for Future Generations

Follow The Money

"It has to start somewhere. It has to start sometime. What better place than here? What better time than now?"

Pedal and Plow

Cycling across South America to to discover what agriculture can be


The important thing is not to stop questioning. Curiosity has it's own reason for existing.


Patrick Sudlow's blog

The Common Constitutionalist - Let The Truth Be Known

Politics, current events, human interest & some humor

Midwest Naturalist

Living in harmony with our creator, his creation and all living things.

You Evolving

Science, Adventure, Philosophy, Personal Evolution

Road To Abundance

The Earth Is Full and There is More Than Enough to Spare


Ocean News & Views

Coal Action Network Aotearoa

Keep the Coal in the Hole!

Precarious Climate

A call for urgent action on climate change


“During times of universal deceit, telling the truth becomes a revolutionary act” – George Orwell

Earth Report

Global Disaster Watch - An Overview

The Survival Place Blog

Surviving The World As We Know It

manchester climate monthly

To inform, inspire and involve


Observing the world of renewable energy and sustainable living

%d bloggers like this: