Global warming alarmists frequently claim the last decade or two is the warmest ever. However, the 1930s were just as warm and going even farther back shows that the naturally cyclical global temperature was even warmer than now.
Chinese researches have reconstructed sea surface temperatures (SST) from the Roman Warm Period (centered around 50 A.D.) and the Medieval Climate Anomaly (centered around 990 A.D.) by using the proxy of Strontium/Calcium ratios and Oxygen-18 values of Tradacna gigas (giant clam) shells collected from the northern South China Sea. The results are summarized by CO2Science.org here.
They found that the mean annual sea surface temperature of the 80-year periods centered on the Medieval Climate Anomaly were 0.8 C warmer than now and sea surface temperatures centered on the Roman Warm Period were 1.4°C higher than the mean SST during the AD 1994-2005 portion of the Current Warm Period. Likewise, they also report that the mean summer SSTs of the Medieval Climate Anomaly and Roman Warm Period were, respectively, 0.2 C and 1.0°C higher than that of the current warm period, while the mean winter SSTs of the Medieval Climate Anomaly and Roman Warm Period were, respectively, 1.3 C and 1.8°C higher than that of the current warm period.
This means that IPCC claims that recent decades were the warmest in the past 1300 years are not true.
The results of the current study back up several other studies which found similar results. The paper is: Yan, H., Sun, L., Shao, D., Wang, Y. and Wei, G. 2014, Higher sea surface temperature in the northern South China Sea during the natural warm periods of late Holocene than recent decades. Chinese Science Bulletin 59: 4115-4122.
This and other studies provide more evidence that warming of the late 20th Century is nothing unusual and well within the range of natural variation. These studies also show that carbon dioxide has little influence on global temperature.
The next time someone claims that the X hottest years occurred recently, point them to this post. Point them also to this article: Geologic History: PETM when it really got hot which begins:
“The United Nation’s IPCC and other climate alarmists say all hell will break loose if the global temperature rises more than an additional 2 C (3.6 F). That number, by the way, is purely arbitrary with no basis in science. It also ignores Earth’s geologic history which shows that for most of the time global temperatures have been much warmer than now. Let’s look back at a time when global temperatures are estimated to have been as much as 34 F warmer than they are now. Hell didn’t break loose then.”