• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer

RealClimate

Climate science from climate scientists...

  • Home
  • Start here
  • Contributors
  • Archives
You are here: Home / Archives for mike

mike

Weren’t temperatures warmer than today during the “Medieval Warm Period”?

8 Dec 2004 by mike

Translations: (Français)

This is one of a number of popular myths regarding temperature variations in past centuries. At hemispheric or global scales, surface temperatures are believed to have followed the “Hockey Stick” pattern, characterized by a long-term cooling trend from the so-called “Medieval Warm Period” (broadly speaking, the 10th-mid 14th centuries) through the “Little Ice Age” (broadly speaking, the mid 15th-19th centuries), followed by a rapid warming during the 20th century that culminates in anomalous late 20th century warmth. The late 20th century warmth, at hemispheric or global scales, appears, from a number of recent peer-reviewed studies, to exceed the peak warmth of the “Medieval Warm Period”. Claims that global average temperatures during Medieval times were warmer than present-day are based on a number of false premises that a) confuse past evidence of drought/precipitation with temperature evidence, b) fail to disinguish regional from global-scale temperature variations, and c) use the entire “20th century” to describe “modern” conditions , fail to differentiate between relatively cool early 20th century conditions and the anomalously warm late 20th century conditions.

Filed Under: Climate Science, FAQ, Paleoclimate

OK, But we do know it was warmer than present 6000 years ago, don’t we?

8 Dec 2004 by mike

Translations: (Français)

This is yet another oft-repeated but problematic assertion based in this case on the mis-characterization of the so-called Mid-Holocene Climatic Optimum” or “Mid-Holocene Warm Period”. Paleoclimate experts now know that the mid-Holocene warmth centered roughly 8000 to 6000 years ago was probably restricted to high latitudes and certain seasons (summer in the Northern Hemisphere and winter in the southern hemisphere). Because much of the early paleoclimate evidence that was available (for example, fossil pollen assemblages) came from the Northern Hemisphere extratropics, and is largely reflective of summer conditions, decades ago some scientists believed that this was a time of globally warmer conditions. More abundant evidence now demonstrates, for example, that the tropical regions were cooler over much of the year.

[Read more…] about OK, But we do know it was warmer than present 6000 years ago, don’t we?

Filed Under: Climate Science, FAQ, Paleoclimate

Michael E. Mann

6 Dec 2004 by mike

Dr. Michael E. Mann is Presidential Distinguished Professor in the Department of Earth and Environmental Science at the University of Pennsylvania, with a secondary appointment in the Annenberg School for Communication. He is director of the Penn Center for Science, Sustainability, and the Media (PCSSM).

Dr. Mann received his undergraduate degrees in Physics and Applied Math from the University of California at Berkeley, an M.S. degree in Physics from Yale University, and a Ph.D. in Geology & Geophysics from Yale University. His research involves the use of theoretical models and observational data to better understand Earth’s climate system.

Dr. Mann was a Lead Author on the Observed Climate Variability and Change chapter of the Intergovernmental Panel on Climate Change (IPCC) Third Scientific Assessment Report in 2001 and was organizing committee chair for the National Academy of Sciences Frontiers of Science in 2003. He has received a number of honors and awards including NOAA’s outstanding publication award in 2002 and selection by Scientific American as one of the fifty leading visionaries in science and technology in 2002. He contributed, with other IPCC authors, to the award of the 2007 Nobel Peace Prize. He was awarded the Hans Oeschger Medal of the European Geosciences Union in 2012 and was awarded the National Conservation Achievement Award for science by the National Wildlife Federation in 2013. He made Bloomberg News’ list of fifty most influential people in 2013. In 2014, he was named Highly Cited Researcher by the Institute for Scientific Information (ISI) and received the Friend of the Planet Award from the National Center for Science Education. He received the Stephen H. Schneider Award for Outstanding Climate Science Communication from Climate One in 2017, the Award for Public Engagement with Science from the American Association for the Advancement of Science in 2018 and the Climate Communication Prize from the American Geophysical Union in 2018. In 2019 he received the Tyler Prize for Environmental Achievement and in 2020 he received the World Sustainability Award of the MDPI Sustainability Foundation. He was elected to the U.S. National Academy of Sciences in 2020. He is a Fellow of the American Geophysical Union, the American Meteorological Society, the Geological Society of America, the American Association for the Advancement of Science, and the Committee for Skeptical Inquiry. He is also a co-founder of the award-winning science website RealClimate.org.

Dr. Mann is author of more than 200 peer-reviewed and edited publications, numerous op-eds and commentaries, and four books including Dire Predictions: Understanding Climate Change, The Hockey Stick and the Climate Wars: Dispatches from the Front Lines, The Madhouse Effect, The Tantrum that Saved the World and The New Climate War; He is co-founder of RealClimate.

More information about his research and publication record can be found here.

All posts by mike.

Filed Under: Contributor Bio's

Temperature Variations in Past Centuries and the so-called "Hockey Stick"

4 Dec 2004 by mike

Translations: (Français)

Instrumental data describing large-scale surface temperature changes are only available for roughly the past 150 years. Estimates of surface temperature changes further back in time must therefore make use of the few long available instrumental records or historical documents and natural archives or ‘climate proxy’ indicators, such as tree rings, corals, ice cores and lake sediments, and historical documents to reconstruct patterns of past surface temperature change. Due to the paucity of data in the Southern Hemisphere, recent studies have emphasized the reconstruction of Northern Hemisphere (NH) mean, rather than global mean temperatures over roughly the past 1000 years.

[Read more…] about Temperature Variations in Past Centuries and the so-called "Hockey Stick"

Filed Under: Climate modelling, Climate Science, Greenhouse gases, Paleoclimate, Sun-earth connections

Myth vs. Fact Regarding the "Hockey Stick"

4 Dec 2004 by mike

Translations: (Español)

Numerous myths regarding the so-called "hockey stick" reconstruction of past temperatures, can be found on various non-peer reviewed websites, internet newsgroups and other non-scientific venues. The most widespread of these myths are debunked below:

[Read more…] about Myth vs. Fact Regarding the "Hockey Stick"

Filed Under: Paleoclimate

False Claims by McIntyre and McKitrick regarding the Mann et al. (1998) reconstruction

4 Dec 2004 by mike

A number of spurious criticisms regarding the Mann et al (1998) proxy-based temperature reconstruction have been made by two individuals McIntyre and McKitrick ( McIntyre works in the mining industry, while McKitrick is an economist). These criticisms are contained in two manuscripts (McIntyre and McKitrick 2003 and 2004–the latter manuscript was rejected by Nature; both are collectively henceforth referred to as “MM”). MM claim that the main features of the Mann et al (1998–henceforth MBH98) reconstruction, including the “hockey stick” shape of the reconstruction, are artifacts of a) the centering convention used by MBH98 in their Principal Components Analysis (PCA) of the North American International Tree Ring Data Bank (‘ITRDB’) data, b) the use of 4 infilled missing annual values (AD 1400-1403) in one tree-ring series (the ‘St. Anne’ Northern Treeline series), and c) the infilling of missing values in some proxy data between 1972 and 1980. Each of these claims are demonstrated to be false below. [Read more…] about False Claims by McIntyre and McKitrick regarding the Mann et al. (1998) reconstruction

Filed Under: Paleoclimate

CO2 Fertilization

28 Nov 2004 by mike

It has sometimes been argued that the earth’s biosphere (in large part, the terrestrial biosphere) may have the capacity to sequestor much of the increased carbon dioxide (CO2) in the atmosphere associated with human fossil fuel burning. This effect is known as “CO2 fertilization” because, in the envisioned scenario, higher ambient CO2 concentrations in the atmosphere literally “fertilize” plant growth. Because plants in turn, in the process of photosynthesis, convert CO2 into oxygen, it is thus sometimes argued that such “co2 fertilization” could potentially provide a strong negative feedback on changing CO2 concentrations.

[Read more…] about CO2 Fertilization

Filed Under: Glossary

Rutherford et al 2005 highlights

22 Nov 2004 by mike

The claims of McIntyre and McKitrick regarding the Mann et al (1998) temperature reconstruction have recently been discredited by the following peer-reviewed article to appear in the American Meteorological Society journal, “Journal of Climate“:

Rutherford, S., Mann, M.E., Osborn, T.J., Bradley, R.S., Briffa, K.R., Hughes, M.K., Jones, P.D., Proxy-based Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Methodology, Predictor Network, Target Season and Target Domain, Journal of Climate, in press (2005).

Key excerpts from the article are provided below: [Read more…] about Rutherford et al 2005 highlights

Filed Under: Supplemental data

PCA details

22 Nov 2004 by mike

PCA of the 70 North American ITRDB Tree-ring Proxy Series used by Mann et al (1998)

[Read more…] about PCA details

Filed Under: Supplemental data

  • « Go to Previous Page
  • Go to page 1
  • Interim pages omitted …
  • Go to page 3
  • Go to page 4
  • Go to page 5

Primary Sidebar

Email Notification

get new posts sent to you automatically (free)
Loading

Recent Posts

  • 2022 updates to the temperature records
  • Unforced variations: Jan 2023
  • The water south of Greenland has been cooling, so what causes that?
  • Unforced variations: Dec 2022
  • Serious mistakes found in recent paper by Connolly et al.
  • Unforced variations: Nov 2022

Our Books

Book covers
This list of books since 2005 (in reverse chronological order) that we have been involved in, accompanied by the publisher’s official description, and some comments of independent reviewers of the work.
All Books >>

Recent Comments

  • Carbomontanus on The water south of Greenland has been cooling, so what causes that?
  • Don Williams on 2022 updates to the temperature records
  • Carbomontanus on The water south of Greenland has been cooling, so what causes that?
  • John Pollack on 2022 updates to the temperature records
  • JCM on 2022 updates to the temperature records
  • Ray Ladbury on 2022 updates to the temperature records
  • Carbomontanus on Unforced variations: Jan 2023
  • Carbomontanus on 2022 updates to the temperature records
  • Victor on 2022 updates to the temperature records
  • Victor on 2022 updates to the temperature records
  • macias shurly on 2022 updates to the temperature records
  • Victor on 2022 updates to the temperature records

Footer

ABOUT

  • About
  • Translations
  • Privacy Policy
  • Contact Page
  • Login

DATA

  • Data Sources
  • Climate model projections compared to observations

INDEX

  • Acronym index
  • Index

Realclimate Stats

1,290 posts

8 pages

229,489 comments

Copyright © 2023 · RealClimate is a commentary site on climate science by working climate scientists for the interested public and journalists.