New Paper: N. Hemisphere Temps Rose 4–5°C Within ‘A Few Decades’ 14,700 Years Ago – 40 Times Faster Than Today’s Rates

By: - Climate DepotApril 14, 2017 10:29 AM

 Temperatures, Sea Levels ‘Naturally’ Rise

 30 – 40 Times Faster Than Today’s Rates

Modern Temperatures Only Rising 0.05°C/Decade

Since 1850, CO2 concentrations have risen from 285 ppm to 400 ppm.  During these ~165 years, the IPCC has concluded that surface temperatures have warmed by 0.78°C.  This is a warming rate of only 0.05°C per decade for 1850-2012 — which happens to be the same rate of warming over the 1998-2012 period.

IPCC AR5 (2013):     “The globally averaged combined land and ocean surface temperature data as calculated by a linear trend, show a warming of 0.85°C over the period 1880 to 2012, when multiple independently produced datasets exist. The total increase between the average of the 1850–1900 period and the 2003–2012 period is 0.78 °C, based on the single longest dataset available 4 (see Figure SPM.1). … [T]he rate of warming over the past 15 years (1998–2012; 0.05 °C per decade), which begins with a strong El Niño, is smaller than the rate calculated since 1951 (1951–2012; 0.12 °C per decade).”

Modern Sea Levels Only Rising 0.17 Of A Meter/Century

IPCC AR5 (2013):     “[T]he rate of global averaged sea level rise was 1.7 mm yr between 1901 and 2010

Historical Hemispheric Temperatures Rose 2.0°C/Decade

According to a new paper, the Bølling Warming event 14,700 years ago raised the surface temperature for the entire Northern Hemisphere by 4 to 5°C within a few decades.  This is a hemispheric warming rate of approximately 2.0°C per decade, which is 40 times faster than the 0.05 °C per decade global warming rate since 1850 (and 1998).

Historical Sea Levels Rose 5.3 Meters/Century

Central Greenland’s surface temperatures rose by as much as 12°C during this time frame (14,700 years ago to 14,500 years ago).  Consequently, glaciers and ice sheets disintegrated rapidly and sea levels rose by about 18 meters (“12-22 m”) in 340 years.  An 18 m rise in 340 years is the equivalent of 5.3 meters per century, which is more than 30 times faster than the rate of sea level change (0.17 m per century) between 1901 and 2010.

Ivanovic et al., 2017     “During the Last Glacial Maximum 26–19 thousand years ago (ka), a vast ice sheet stretched over North America [Clark et al., 2009]. In subsequent millennia, as climate warmed and this ice sheet decayed, large volumes of meltwater flooded to the oceans [Tarasov and Peltier, 2006; Wickert, 2016]. This period, known as the “last deglaciation,” included episodes of abrupt climate change, such as the Bølling warming [~14.7–14.5 ka], when Northern Hemisphere temperatures increased by 4–5°C in just a few decades [Lea et al., 2003; Buizert et al., 2014], coinciding with a 12–22 m sea level rise in less than 340 years [5.3 meters per century] (Meltwater Pulse 1a (MWP1a)) [Deschamps et al., 2012].”

Bølling Warming/Sea Level Rise Occurred With Stable CO2

CO2 record for 25 kya-present courtesy of Kawamura et al., 2003

Greenland Warmed By 10°C Within 3 Years 14,700 Years Ago

Steffensen et al., 2008
     High-Resolution Greenland Ice Core Data Show Abrupt Climate Change Happens in Few Years 

“A northern shift of the Intertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.”

“The d18O warming transition at 14.7 ka [14,700 years ago] was the most rapid and occurred within a remarkable 3 years, whereas the warming transition at 11.7 ka [11,700 years ago] lasted 60 years; both correspond to a warming of more than 10 K.”

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Modern rates of temperature change and sea level rise are quite modest and unremarkable relative to the magnitude of the changes in the geological past (that are 30 to 40 times larger or faster).  The abrupt and pronounced historical temperature and sea level rise events occurred without any significant changes in atmospheric CO2 levels.

In contrast, during the last 100 to 150 years there has been a dramatic rise in anthropogenic CO2 emissions and atmospheric CO2 concentrations…but no accompanying dramatic rise in temperatures or sea level.

Thus, the conceptualization that human activity or CO2 concentration changes are the primary drivers of temperature changes and sea level rise does not  seem to be supported by the geological evidence.

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