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Another Day, another California Global Warming Scare



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An editorial in today’s Sacramento Bee tells Californians to expect their great-grandchildren to be submerged by sea level rise due to human greenhouse-gas emissions:

How high will these oceans rise? Some computer models show that, without a significant reduction in greenhouse gases, the Greenland ice sheet could melt sometime after 2100. Such a steady melt-off would lead to a 7-meter (23-foot) increase in sea levels, according to the IPCC report. That would submerge most of San Diego, San Francisco and Los Angeles. Tidal action would swamp most of Sacramento.

Unfortunately, the Bee’s editorial writers left out a few pesky details. First, the computer models that predict melting of the Greenland ice sheet were run with the assumption that the CO2 concentration in the atmosphere starts out and stays at four times the pre-industrial level and nearly three times the current level (IPCC Working Group I (WG I) report, p. 830). Even if humans continue to get their energy mainly from fossil fuels, it would take 150 years or more for atmospheric CO2 to rise this high.

Second, the Bee’s “sometime after 2100″ really means several centuries after 2100. Even with atmospheric CO2 at three times current level, the models say it would take 270 years for Greenland to lose even 20% of its ice, and more than 1,700 years to lose 80% of its ice (WG I, p. 830).

The Bee fails to mention a few more inconvenient facts. Greenland was warmer than it is now for several long periods during the last few thousand years (for example, the middle of the 20th Century, the Medieval Warm Period, and the mid-Holocene several thousand years ago) yet Greenland’s ice didn’t flow into the ocean.

The Bee’s editorial wheels also fall off in its discussion of climate change impacts on California. For example, the Bee says

Earlier this year, some people scoffed when the Independent Science Board of the Bay-Delta Authority said the state should prepare for 28 to 39 inches of sea level rise by 2100. The latest IPCC report suggests that those forecasts are on target, with perilous consequences for the Delta and the state’s water systems.

But the top of IPCC’s range for 21st Century sea-level rise is 23 inches.1 More importantly from a California perspective, we have actual long-term trend data on sea-level at San Francisco, which show that sea level has been flat for the last three decades or so, after rising steadily from the 1920s through the 1970s (see this graph of NOAA tide gauge data for San Francisco). In other words, sea level was already rising near California before human GHG emissions could have been a cause (only about 10% of all human CO2 emissions were emitted before 1920), and sea level has stopped rising near California during a period when human GHG emissions are supposed to be increasing the rate of sea level rise.

The Bee claims “Sea levels have risen about a half-foot in the last century, and are now rising even faster.” The first half is true, but is misleading in implying that this rise is due to human greenhouse-gas emissions. World-average sea level was already rising at the beginning of the 20th century–well before human GHG emissions could have been the cause.

The Bee is correct that, according to the IPCC, the rate of sea level rise increased from 1993-2003 when compared with previous decades. But ten years isn’t much to hang your hat on. The IPCC itself recognizes this, stating on page 387 of the Working Group I report “It is unknown whether the higher rate [of sea-level rise] in 1993 to 2003 is due to decadal variability or an increase in the longer-term trend.” This cautionary nuance is well taken, as recent research suggests (1) the rate of sea-level rise slowed between the first and second half of the 20th Century, and (2) the IPCC report overstates by about 40% the rate of sea-level rise during the 20th Century.2

The Bee’s editors would have known they were misinforming their readers if they’d taken the time to look at the IPCC’s actual reports and the contrary evidence omitted by the IPCC. Instead, they relied only on what climate alarmists say is in the IPCC’s reports and assumed incorrectly that the IPCC includes all relevant evidence. Like most other journalists, the Bee’s editors are only too willing to run with falsehoods that fit their knee-jerk appetite for environmental scares.

1. The IPCC’s estimate includes melting of land-bound ice and thermal expansion of the oceans, but excludes dynamical changes in ice flow–meaning it excludes the possibility of, for example, the Antarctic ice sheets sliding into the sea. However, recent research suggests the world’s major ice sheets are dynamically stable. See, for example, R. B. Alley et al., “Effect of Sedimentation on Ice- Sheet Grounding-Line Stability,” Science 315, no. 5820 (2007): 1838–41; S. Anandakrishnan et al., “Discovery of Till Deposition at the Grounding Line of Whillans Ice Stream,” Science 315, no. 5820 (2007): 1835–38; J. B. Anderson, “Climate Change: Ice Sheet Stability and Sea-Level Rise,” Science 315, no. 5820 (2007): 1803–1804; A. Mackintosh et al., “Exposure Ages from Mountain Dipsticks in Mac. Robertson Land, East Antarctica, Indicate Little Change in Ice-Sheet Thickness since the Last Glacial Maximum,” Geology 35, no. 6 (2007): 551–54; and E. Willerslev et al., “Ancient Biomolecules from Deep Ice Cores Reveal a Forested Southern Greenland,” Science 317, no. 5834 (2007): 111–14.

2. The first of these two journal articles (Holgate (2007)) was accepted by Geophysical Research Letters in November 2006 and published on January 4, 2007, nearly a month before the IPCC Working Group I report was released on February 2, 2007. While this perhaps does not provide much lead time for inclusion in a major report, the WG I report cites many other papers with 2007 publication dates, suggesting that lead time was not the main factor in determining what evidence the IPCC elected to include and exclude from its reports. In any case, Holgate (2007), as well as Woppelmann et al. (2007) (the second paper cited above), and much other contrary evidence was certainly available in time to be considered in the IPCC’s Synthesis Report, which was just released in November.



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