What is Berkeley Earth Surface Temperature?
Why is the work being done by Berkeley Earth important?
Who is carrying out this work?
What is project chair Richard Muller's expertise in climate?
What exactly has Berkeley Earth Surface Temperature done so far?
How did the project come about?
Who is funding the project?
It appears that Berkeley Earth's analysis shows a temperature rise greater than others had previously published. Is this so? Can you explain?
Has Global Warming Stopped?
Do Judith Curry and Richard Muller disagree?
What is new about the statistical approach used?
There have been many criticisms of station quality. How can you be sure results will be reliable if you are including stations that do not meet NOAA's criteria for station quality?
Why didn't Berkeley Earth wait for peer review?
Is it time now to end global warming skepticism?
What is next for Berkeley Earth?
Do you have a newsletter? How can I stay up to date with Berkeley Earth's ongoing work?
Is there a reuse policy for using information and media presented by Berkeley Earth?
What is Berkeley Earth Surface Temperature?
Berkeley Earth Surface Temperature aims to contribute to a clearer understanding of global warming based on a more extensive and rigorous analysis of available historical data. The study has reviewed data from over 39,000 temperature measurement stations across the globe. This is more than five times the 7,280 stations found in the Global Historical Climatology Network Monthly data set (GHCN-M) that has served as the focus of many climate studies to date.
Why is the work being done by Berkeley Earth important?
Existing data used to show global warming have met with much criticism. The Berkeley Earth project attempts to resolve current criticism of the former temperature analyses by making available an open record to enable rapid response to further criticism and suggestions. Our results include our best estimate for the global temperature change and our estimates of the uncertainties in the record.
We believe that science is nonpartisan and our interest is in getting a clear view of the pace of climate change in order to help policy makers to evaluate and implement an effective response. In choosing team members, we engage people whose primary interests are finding answers to the current issues and addressing the legitimate concerns of the critics on all sides. None of the scientists involved has taken a public political stand on global warming.
Who is carrying out this work?
The project is headed by Richard Muller and the main scientific work is carried out by Robert Rohde. Richard Muller is a Professor of Physics at the University of California at Berkeley, Faculty Senior Scientist at the Lawrence Berkeley Laboratory, and President of Muller & Associates LLC. Robert Rohde is a scientist who obtained his PhD in experimental/theoretical physics at the University of California at Berkeley. His expertise includes the analysis of large data sets, with estimates of statistical and systematic effects. Together they have co-authored a series of papers on the analysis of bio diversity in the fossil record.
A full list of the project's team members is available here.
What is project chair Richard Muller's expertise in climate?
Richard Muller's published works on climate have appeared in some of the most prestigious peer-reviewed journals including:
- Science (vol. 277, pp 215-218, 11 July 1997; vol. 288, p 2143-2144, 23 June 2000).
- Proceedings of the US National Academy of Sciences (vol. 94, pp 8329-8334, Aug 5, 1997).
- Geology (vol. 25, pp. 3-6, 1997; vol. 25, pp. 859-861, 1997).
- Paleoceanography (vol. 17, pp. 2-1 to 2-12, 2002).
- Geoch. Cosmochim. Acta (vol. 67, pp 751-763, 2003).
- Nature (vol.377, pp 107-108, 14 September 1995).
and also in other journals such as Eos. He has been active in the American Geophysical Union on climate research, and wrote “Ice Ages and Astronomical Causes”, a technical book published by Springer.
Richard was also deeply involved in the hockey stick issue, and was a named referee chosen to review the report of the National Research Council of the US National Academy of Sciences.
What exactly has Berkeley Earth Surface Temperature done so far?
The Berkeley Earth Surface Temperature has set out to:
- Merge existing surface station temperature data sets into a new comprehensive raw data set with a common format that could be used for weather and climate research
- Review existing temperature processing algorithms for averaging, homogenization, and error analysis to understand both their advantages and their limitations
- Develop new approaches and alternative statistical methods that may effectively remove some of the limitations present in existing algorithms
- Create and publish a new global surface temperature record and associated uncertainty analysis
- Provide an open platform for further analysis by publishing our complete data and software code as well as tools to aid both professional and amateur exploration of the data
The Berkeley Earth team has released four preliminary papers with our findings, together with our data base and analysis programs. They are currently available here.
Our papers have been sumbitted to peer reviewed journals, and we are making them available to the public in order to invite additional scrutiny.
How did the project come about?
The Berkeley Earth project was created in 2010, by Richard Muller and his daughter Elizabeth Muller who had been previously collaborating on energy and climate issues. Together they observed a real need for a new project to analyze current global surface temperature records in order to respond to concerns of critics and calm the debate about global warming. After connecting with Michael Ditmore, the Executive Director of Novim (a non-profit funded by donors), and joining with lead scientist Robert Rohde, Berkeley Earth was created as a project within Novim.
Who is funding the project?
A complete list of our donors and the amounts that they contributed is available here. We have received financial support totaling more than $600,000 from the Folger Fund, the Lawrence Berkeley National Laboratory, the Fund for Innovative Climate and Energy Research (created by Bill Gates), the Bowes Foundation, the Koch Foundation, and the Getty Foundation. Together, the people who created these organizations span a wide range of political views. We have also received funding from a number of private individuals, totaling $14,500 at this time.
All donations were provided as unrestricted educational grants and donors have no influence over our methodology or our published results. Our results have now been made public and will be presented with full transparency, and our data are available to those who wish to carry out their own analysis.
A statement from the Charles Koch Foundation on the Berkeley Earth research is available here.
It appears that Berkeley Earth's analysis shows a temperature rise greater than others
had previously published. Is this so? Can you explain?
Berkeley Earth has not yet begun to analyze ocean temperatures (we hope to do this in the next year), so the plotted data is land only. Land warms more than oceans, so when we include the ocean we expect the total global warming to be less.
We started with the land data for several reasons:
- It is the data that is most greatly affected by the most contentious issues: data selection bias, urban heat island, and station integrity issues. These are major concerns that we wanted to address.
- The temperature rise on land is greater than in the oceans, greatly due to the oceans distribution of heat over the mixed layer thereby reducing the temperature rise. Because land keeps the heat mostly on the surface, the land temperature is actually more sensitive to greenhouse gases than is the world temperature.
- With 1.6 billion measurements, culling land temperature data was a major effort. It made sense to divide the project into two stages.
Has Global Warming Stopped?
Some people have suggested that there has been no global warming over the
past 13 years, and they ask whether our land-only analysis verifies that.
The graph shows the results of our analysis with 1-year averaging (to smooth
it) for the last 6 decades so you can better see the period in question.
The blue curve is the result of our analysis, and the grey lines represent
our 95% confidence limits.
The large fluctuations up and down that take place every few years correlate
very strongly with the North Atlantic temperatures (the AMO index) and with
El Nino (ENSO index 3.4). See our paper on "Decadal Variations in the
Global Atmospheric Land Temperatures" for analysis of that. The presence of
these fluctuations makes any strong extrapolations from short-term behavior
uncertain.
Some people draw a line segment covering the period 1998 to 2010 and argue
that we confirm no temperature change in that period. However, if you did
that same exercise back in 1995, and drew a horizontal line through the data
for 1980 to 1995, you might have falsely concluded that global warming had
stopped back then. This exercise simply shows that the decadal fluctuations
are too large to allow us to make decisive conclusions about long term
trends based on close examination of periods as short as 13 to 15 years.
Do Judith Curry and Richard Muller disagree?
Below is a joint statement by Judith Curry and Richard Muller:
In recent days, statements we've made to the media and on blogs have been
characterized as contradictory. They are not.
We have both said that the global temperature record of the last 13 years
shows evidence suggesting that the warming has slowed. Our new analysis of
the land-based data neither confirms nor denies this contention. If you look
at our new land temperature estimates, you can see a flattening of the rise,
or a continuation of the rise, depending on the statistical approach you
take.
Continued global warming "skepticism" is a proper and a necessary part of
the scientific process. The Wall St. Journal Op-Ed by one of us (Muller)
seemed to take the opposite view with its title and subtitle: "The Case
Against Global-Warming Skepticism -- There were good reasons for doubt,
until now." But those words were not written by Muller. The title and the
subtitle of the submitted Op-Ed were "Cooling the Warming Debate - Are you a
global warming skeptic? If not, perhaps you should be. Let me explain
why." The title and subtitle were changed by the editors without consulting
or seeking permission from the author. Readers are encouraged to ignore the
title and read the content of the Op-Ed.
We do not agree with each other on every feature of climate change. We have
had vigorous discussions, for example, on the proper way to analyze
hurricane records. Such disagreements are an essential part of the
scientific process.
What is new about the statistical approach used?
The central challenge of global temperature reconstruction is to take spatially and temporally diverse data exhibiting varying levels of quality and construct a global index series that can track changes in the mean surface temperature of the Earth. This challenge presents no easy solution and we believe that there is inherent value in comparing different approaches to this problem as well as understanding the weaknesses intrinsic to any given approach. Thus, we have studied both the existing methodologies for averaging and homogenizing data as well as look for new approaches whose features seem to incorporate valuable alternatives to the existing methods.
The statistical methods that we use have been developed by Robert Rohde in close collaboration with David Brillinger, a Professor of Statistics at the University of California at Berkeley, and the other team members. They include the statistical approach called Kriging (a process which allows us to combine fragmented records in an optimum way), the scalpel (which identifies discontinuities and cuts the data at those points) and weighting (in which the program estimates numerically the reliability of a data segment and applies a weight that reduces the contribution of the poor samples). The methods all use raw data as input. There are no manual corrections applied; all the weights and scalpel points are determined using automated and reproducible methods.
Our algorithms aim to:
- Make it possible to exploit relatively short (e.g. a few years) or discontinuous station records. Rather than simply excluding all short records, we prefer to design a system that allows short records to be used with a low - but non-zero - weighting whenever practical.
- Avoid gridding. All three major research groups currently rely on spatial gridding in their averaging algorithms. As a result, the effective averages may be dependent on the choice of grid pattern and may be sensitive to effects such as the change in grid cell area with latitude. Our algorithms eliminate explicit gridding entirely.
- Place empirical homogenization on an equal footing with other averaging. We distinguish empirical homogenization from evidence-based homogenization. Evidence-based adjustments to records occur when secondary data and/or metadata is used to identify problems with a record and to then propose adjustments. By contrast, empirical homogenization is the process of comparing a record to its neighbors to detect undocumented discontinuities and other changes. This empirical process performs a kind of averaging as local outliers are replaced with the basic behavior of the local group. Rather than regarding empirical homogenization as a separate preprocessing step, we plan to incorporate empirical homogenization as a process that occurs simultaneously with the other averaging steps.
- Provide uncertainty estimates for the full time series through all steps in the process.
A detailed description of the statistical methods used by Berkeley Earth can be found in the draft paper "Berkeley Earth Temperature Averaging Process", available here.
There have been many criticisms of station quality. How can you be sure your results will be reliable if you are including stations that do not meet NOAA's criteria for station quality?
One of the elements that we have analyzed is temperature records from only the very best sites (as classified by Anthony Watts and his team) contrasted with the poorer sites. This analysis is in the paper "Earth Atmospheric Land Surface Temperature and Station Quality in the United States", available here.
Additionally, each of our 39,028 sites has been classified as urban or rural using the map published by the Modis satellite team, and have also used that classification to look for differences. The results of that analysis are in the paper "Influence of Urban Heating on the Global Temperature Land Average", available here.
Why didn't Berkeley Earth wait for peer review?
Some people think that peer review consists of submitting a paper to a journal and waiting for the anonymous comments of referees. Traditional peer review is much broader than that and much more open. In science, when you have a new result, your first step is to present it to your colleagues by giving presentations, talks at local and international conferences, colloquia, and by sending out "preprints." In fact, every academic department in the sciences had a preprint library where people would read up on the latest results. If they found something to disagree with, they would talk to or write the authors. Preprint libraries were so popular that, if you found someone was not in the office or lab, the first place you would search would be in the preprint library. Recently these rooms have disappeared, their place taken over by the internet. The biggest preprint library in the world now is a website, arXiv.org.
Such traditional and open peer review has many advantages. It usually results in better papers in the archival journals, because the papers are widely examined prior to publication. It does have a disadvantage, however, that journalists can also pick up preprints and report on them before the traditional peer-review process is finished.
Perhaps because of the media picking up on talks and preprints, a few journals made a new rule: they will not publish anything that is distributed as a preprint or that is discussed openly in a meeting or colloquium. This policy has resulted in more attention to several journals, but the restrictive approach had a detrimental effect on the traditional peer review system. Some fields of science, for example String Theory, objected so strongly that they refuse to publish in these journals, and they put all their papers online immediately.
The best alternative would be to have the media hold back and not report preprint material. Unfortunately they refuse to do that. The situation is made more difficult by the fact that many of the media misreport the content of the preprints. For that reason Berkeley Earth has tried to answer the questions given to us by the media, in hopes that our work will be more accurately reported. The two page summary of findings is also meant to help ensure that the media reports accurately reflect the content of our papers.
Is it time now to end global warming skepticism?
Our study addressed only one area of the concerns: was the temperature rise on land improperly affected by the four key biases (station quality, homogenization, urban heat island, and station selection)? The answer turned out to be no – but they were questions worthy of investigation. Berkeley Earth has not addressed issues of the tree ring and proxy data, climate model accuracy, or human attribution.
What is next for Berkeley Earth?
As a next step, Berkeley Earth plans to address the total warming of the oceans, with a view to obtaining a more accurate figure for the total amount of global warming observable.
Do you have a newsletter? How can I stay up to date with Berkeley Earth's ongoing work?
You can sign up for Berkeley Earth email alerts here.
Is there a reuse policy for using information and media presented by Berkeley Earth?
The authors of the material available on the Berkeley Earth website (www.berkeleyearth.org) grant permission (free of charge) to authors, readers and third parties to reproduce their materials as part of another publication or entity with proper sourcing to Berkeley Earth and by additionally providing a link to the Berkeley Earth website ( http://www.berkeleyearth.org ).
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