OT: Rapid temperature changes

Using oxygen isotope analysis on stalagmites in a Wisconsin cave, Batchelor et al. discovered rapid temperature swings in the past.

“Using another technique, they identified the isotopes in the tiny layers, revealing that present-day southern Wisconsin experienced a number of very large average temperature swings of up to 10 C (or about 18 F) between 48,000 and 68,000 years ago. Several of the temperature swings occurred over the course of around a decade.”




Dunno, DB2.

Presenting facts that introduce doubt about all the warnings is just unacceptable these days. You need to “follow the science”. Otherwise you’re a “denier” and subject to bad things.

He is no fool who gives what he cannot keep to gain what he cannot lose.


Bob likes to cherry pick science papers, present them with little context, and imply that climate change is overblown and climate science is contradictory. Let’s look a little deeper at the paper in question.

The core of the paper is the authors make new oxygen isotope ratio measurements (δ18O) at Cave of the Mounds (COM), Wisconsin. The measurements are from rocks formed 50-70 thousand years ago during a period of large rapid climate change called Dansgaard–Oeschger (DO) events during the last ice age. Scientists have known about DO events for almost 40 years. The goal of the analysis is to infer temperature from these δ18O measurements.

The authors remind us that δ18O depends on both rainfall and temperature. To estimate temperature, you need to know rainfall. The authors use climate models to estimate rainfall. The same climate models that Bob likes to discredit. The same climate models that show dangerous future warming. If you trust these results, then you trust climate models. If you don’t trust climate models, then you shouldn’t trust these results.

Are large rapid temperature changes a new discovery? No. The authors say

Rapid, ~10 °C warming at COM during DO events is consistent with North American, southern European and Mediterranean pollen reconstructions

So what’s new? What’s new is the location of the data in near the edge of the North American ice sheet.

This record provides close insight into the magnitude and rate of climate changes adjacent to the southern margin of the ice sheet and outside of the North American monsoon region

What caused these large changes? The authors say there are two causes (and are clear that the warming is modelled, not measured, only δ18O is measured)

the modelled annual warming at COM amounts to 8–10 °C for DO event 1 and is attributed to the superposition of climatic responses to the abrupt AMOC recovery and the increase of atmospheric CO2 during DO event 1.

The AMOC (Atlantic Meridional Overturning Circulation) is the part of the thermohaline circulation that has long been known to potentially cause large rapid climate change. This paper provides further evidence of the impact of changes in the AMOC and highlights the concern about potential anthropogenic AMOC changes.

The other cause of the rapid warming is CO2. It has long been known that DO events are correlated with changes in CO2. This paper is yet another piece of evidence on the role CO2 has in controlling climate.

My summary is this article is an interesting study about natural variability of temperature that fills in a hole by documenting temperatures in a new location. The results largely agree with what was already known and adds additional evidence for the reliability of climate models and the importance of CO2. In no way does this study reduce the risk of human climate change.


Nice summary of why this article is in support of existing evidence of human caused climate change and the need to change our behaviors.


This is true. For example, we read in Botkin from 2007:

“Until recently, it was thought that past temperature changes were no more rapid than 1 degree Celsius (°C) per millennium, but recent information from both Greenland and Antarctica, which goes back approximately 400,000 years, indicates that there have been many intervals of very rapid temperature change, as judged by shifts in oxygen isotope ratios. Some of the most dramatic changes (e.g., 7°C to 12°C within approximately 50 years; Macdougall 2006) are actually of greater amplitude than anything projected for the immediate future.”


The American Institute of Physics has a nice set of web pages on the history of climate science. The summary for their webpage on rapid climate change says

By the 20th century, scientists had rejected old tales of world catastrophe, and were convinced that global climate could change only gradually over many tens of thousands of years. But in the 1950s, a few scientists found evidence that some changes in the past had taken only a few thousand years. During the 1960s and 1970s other data, supported by new theories and new attitudes about human influences, reduced the time a change might require to hundreds of years. Many doubted that such a rapid shift could have befallen the planet as a whole. The 1980s and 1990s brought proof (chiefly from studies of ancient ice) that the global climate could indeed shift radically within a century — perhaps even within a decade. And there seemed to be feedbacks that could make warming self-sustaining. Scientists could not rule out possible “tipping points” for an irreversible and catastrophic climate change if greenhouse gas emissions continued to rise.


One also needs to remember that a study of temperature changes at a specific location may fit into a pattern of change globally, but not the same temperatures everywhere … especially when the point of measurement is at the edge of an ice sheet. Way back when, it was not unreasonable to expect a group of hominids to migrate if the weather became problematic … there were few of us around. These days relocating NYC is a wee bit bigger problem.