Monday, July 17, 2017

Myth: No Global Warming for Two Decades

The outline for this post is as follows:
  1. The Myth and Its Flaw
  2. Context and Analysis
  3. Posts Providing Further Information and Analysis
  4. References

This is the "main version" of this post, which means that this post lacks most of my references and citations. If you would like a more comprehensive version with all the references and citations, then please go to the "+References" version of this post.

References are cited as follows: "[#]", with "#" corresponding to the reference number given in the References section at the end of this post.

1.  The Myth and Its Flaw

The myth states that there has been no warming for about two decades.

Purveyors of this myth include Christopher Monckton, Willie Soon, David LegatesJohn Christy, Ted Cruz, Anthony Watts, Patrick Michaels, Paul (Chip) Knappenberger, Judith Curry, Bob Tisdale, Richard Lindzen, Matt Ridley, and Anastasios Tsonis.

The myth's flaw: over the past two decades the ocean and land warmed, as has the lower atmosphere. This warming was reflected in the difference between the amount of energy Earth takes up vs. the amount of energy Earth release.

2. Context and Analysis

Oceans and land warmed over the past two decades. Satellite and weather balloon (radiosonde) analyses also revealed warming of the troposphere, a lower region of the atmosphere where much of Earth's weather occurs. These two decades of warming were reflected in Earth's energy balance, a measure of the amount of energy Earth takes up vs. the amount of energy Earth releases

The figures below illustrate some of this recent warming:

Figure 1: Comparison of ocean temperature records from 1997 to 2015 for different sources, relative to a 1997-2001 baseline. The sources are buoys, the NOAA's (National Ocean and Atmospheric Association) Extended Reconstructed Sea Surface Temperature (ERSST) record for both ERSSTv3b and the updated ERSSTv4, and the European Space Agency Climate Change Initiative (CCI) [1, figure 1].

Figure 2: Comparison of ocean temperature records from 1997 to 2015 for different sources. NOAA's Extended Reconstructed Sea Surface Temperature (ERSST) record for ERSSTv3b and ERSSTv4 are compared to ocean heat measurements from Argo floats. Argo(H2008), Argo(APDRC), and Argo(RG2000) represent three different near-surface temperature data-sets derived from the Argo data. ERSSTv4 data is presented relative to a 1997-2001 baseline, while the other data sources are aligned to the 2005-2007 baseline for ERSSTv4 [1, figure S2]. 

Figure 3: Global, annual, mean surface temperature relative to mean temperature during pre-industrial era (1720 - 1800), or relative to mean temperature from 1986 - 2005 in the case of ERA-Interim, as shown in multiple temperature analyses. Pre-2016 data came from a previous scientific publication [2, figure 5], with later data added in a subsequent analysis [3]. This post-1997 warming trend continues through 2018, as shown using an online tool summarized in a published paper. This is illustrated for HadCRUT4, NOAA GlobalTemp, GISTEMP, BEST, JMA, ERA-Interim, JRA-55, MERRA-2, with MERRA-2 having an anomalously low post-1997 warming trend. HadCRUT4 and NOAA GlobalTemp under-estimate post-1997 warming due to their poorer coverage of the globe.

Figure 4: Global, annual, mean surface temperature relative to mean temperature from 1961 - 1990 [8, figure 1b]. I discuss the temperature trend (especially from the 1940s to the 1970s) in the context of a near-linear carbon-dioxide-induced warming trend, in section 2.10 of "Myth: Attributing Warming to CO2 Involves the Fallaciously Inferring Causation from a Mere Correlation".

Figure 5: Trend in global, monthly, mean surface temperature from 1979 to 2016 relative to baseline of 1981 - 2010, as shown in multiple temperature analyses. The solid green trend-line is represents the trend for 1998 - 2012, while the dotted black trend-line represents the trend for the full period from 1979 - 2016 [4, figure 3].

Figure 6: Version 3.3 and version 4.0 of the Remote Sensing Systems (RSS) near-global lower tropospheric temperature analysis, along with version 5.6 and version 6.0 of the University of Alabama in Huntsville (UAH) near-global lower tropospheric temperature trends. RSS version 4.0 is an update of RSS version 3.3, while UAH version 6.0 is an update of UAH version 5.6. The lower lines (black, gray, red, and pink) indicate temperature relative to a baseline of 1979 - 1981. The upper lines (green and purple) display the difference between the relative temperature values. Quantified trends are from 1979 - 2016 [5].

Figure 7: Near global mid- to upper tropospheric temperature averaged for the UAH, NOAA, and RSS satellite-based analyses [6].

As a 2017 paper noted:

"Rather, the data are fully consistent with a steady global warming trend since the 1970s, superimposed with random, stationary, short-term variability. All recent variations in short-term trends are well within what was to be expected, based on the observed warming trend and the observed variability from the 1970s up to the year 2000 [7]."

This post-1997 warming cannot be accounted for in terms of an ocean cycle known as the El Niño Southern Oscillation, as I discuss in "Myth: El Niño Caused Most Post-1997 Warming". El Niño, however, does cause a more pronounced warming spike in 1998; this spike is greater in the troposphere than at Earth's surface (compare figure 3 to figures 6 and 7) due largely to a short-term "tropospheric hot spot" that I discuss in "Myth: The Tropospheric Hot Spot is a Fingerprint of CO2-induced Warming".

3. Posts Providing Further Information and Analysis

4. References

  1. "Assessing recent warming using instrumentally homogeneous sea surface temperature records"
  2. "Estimating changes in global temperature since the pre-industrial period"
  3. "Guest post: The challenge of defining the ‘pre-industrial’ era"
  4. "A reassessment of temperature variations and trends from global reanalyses and monthly surface climatological datasets"
  5. "A satellite-derived lower tropospheric atmospheric temperature dataset using an optimized adjustment for diurnal effects"
  6. "Tropospheric warming over the past two decades"
  7. "Global temperature evolution: recent trends and some pitfalls"
  8. "Recent United Kingdom and global temperature variations"