Andean glaciers have reduced more than ever throughout Holocene

Glaciers are important indicators of climate change. TO Recent study Posted in the main magazine Science It shows that glaciers in the tropical Andes have now retired further at any other time in the entire Holocene, which covers the entire history of human civilization since the invention of agriculture. These findings are likely to resonate beyond the scientific community, since they firmly support the lawsuit filed by a Peruvian farmer against the RWE energy company, which has returned to court this week.

Paleoclimatologists can determine how long it has been covered by an ice glacier using specific isotope measurements. When rock surfaces are exposed, isotopes are formed such as carbon-14 and beryllium-10 due to cosmic radiation bombardment. However, if the rock is covered by an ice layer, it is protected from this radiation, and these unstable isotopes gradually disappear through radioactive decomposition (with average 5,700 and 1.4 million years old lives, respectively). This method, known as cosmogenic radionucleid dating, has been well established For decades. I found it for the first time 23 years ago during a excursion With experts in glaciers from the Alps of the South of New Zealand.

The new study applied this method to examine several glaciers in the tropical Andes (see Fig. 1).

In rock samples collected at the edges of the glaciers, the researchers found concentrations of isotopes close to zero. From this, they conclude that these rocks must have remained covered by ice throughout the Holocene, protecting them from cosmic radiation. This indicates that these glaciers are most likely smaller today than at least the last 11,700 years.

This finding is aligned with several previous studies that show that temperatures in the tropical Andes have never been warmer during the Holocene than today. For example, the reconstructions of the glacier margin of the quelccaya ice layer show that it has not been smaller than today at least in at least the Last 7,000 years. Temperature reconstructions based on proxy data further support this conclusion.

Global warming means global withdrawal of glaciers

The Andes are no exception: according to current research, today’s average global temperatures are most likely higher than at any other time during All the Holocene. Since an ice age lasted more than 100,000 years before Holocene, today’s temperatures are probably the highest experienced in approximately 120,000 years. This unprecedented warming, which began in the nineteenth century and has arrived so far 1.3–1.4 ° C.It is almost completely driven by human activity, mainly by burning fossil fuels. According to the Intergovernmental Panel on Climate Change (IPCC), the natural factors have contributed very little to recent heating, probably even having a slightly refreshing effect, due to the decrease in solar activity since the mid -twentieth century (a fact reflected in the title of former RWE Fritz Vahrenholt manager, Die Kalte Sonne – The cold sun).

As a result, glaciers worldwide continue lose the dough (See Figure 2). In Germany, only four glaciers remain, after the disappearance of the Southern Schneeferner glacier in September 2022. Soon, there will be no glaciers in Germany at all.

Implications for the RWE case

RWE’s case addresses, among other things, whether the global warming caused by CO₂ emissions is responsible for the severe melting of the glacier, the substantial withdrawal of the glacier in approximately 1.5 km in the last 140 years and the defrosting of Permafrost over the city of Huaraz in Peru. A 2021 Attribution study Posted in respected magazine Geoscience of nature This connection has already demonstrated conclusively; However, RWE seems to continue challenging these findings.

In this context, the new data of Gorin et al. They are particularly relevant. The Queshque glacier, now smaller than at any other time at least the last 11,700 years, is only 40 km from Huaraz, in the same mountain range as the Palcacocha lake (see Fig. 3).

It is very likely that local climate changes in this area differ minimally at the maximum. Although average climatic conditions may vary at short distances due to local topography, weather heating It typically has a correlation radius of more than 1,000 km. Therefore, there is no significant difference in the effects of climate change between Queshque Glacier and Lake Palcacocha.

This region is already experiencing the most significant climate warming in the history of human civilization. It will undoubtedly continue until the global economy achieves climate neutrality, essentially, zero net-zero emissions.

In RWE’s trial, the central problem will be yes, and to what extent, the city of Huaraz and the plaintiff would be affected by a flood of glaciers. A systematic analysis of the floods of Glacial Lake (GLOF) burst in the region has examined 160 events of this type based on satellite images. The findings clearly identify the Andes around Huaraz as an access point for this risk (see Fig. 4).

In addition, this study shows that the frequency of such floods has increased significantly since 1980 (see Fig. 5). Before 1980, there was only one year with more than two registered GLOF: 1970 due to a severe earthquake. However, now there are years repeatedly with 3, 4 or even 5 outbursts in the glacial lake.

One thing is clear: given the existing research, it would be absurd to assume that the risk of an outburst of the Palcacocha lake could be calculated based solely on historical data, without explicitly taking into account the global warming caused by fossil fuels. Anyone suggesting that climate change is not happening in Huaraz, that there are no human fingerprints and, therefore, no connection with most CO₂ emissions can have their reasons to do so. But evidence clearly shows the opposite.