The Greenland Ice Sheet “Tipping Point” That Wasn’t – Watts Up With That?

The recently published paper A Topographically Controlled Tipping Point for Complete Greenland Ice Sheet Melt by Petrini et al. is a textbook example of how climate modeling has transformed from a scientific tool into a mechanism for manufacturing hysteria. Rather than producing objective assessments of future possibilities, this paper constructs a doomsday scenario with all the precision of a weather forecast 10,000 years into the future—making sure to terrify the public just enough to ensure continued research funding and political influence.

Abstract

A major impact of anthropogenic climate change is the crossing of tipping points, which may have severe consequences such as the complete mass loss of the Greenland ice sheet (GrIS). At present, the GrIS is losing mass at an accelerated rate, largely due to a steep decrease in its surface mass balance (SMB; the balance between snow accumulation and surface ablation from melt and associated runoff). Previous work on the magnitude and nature of a threshold for GrIS complete melt remains controversial. Here, we explore a potential SMB threshold for complete melt of the GrIS; the impact and interplay of surface melt and glacial isostatic adjustment (GIA) in determining this threshold; and whether the GrIS exhibits characteristics commonly associated with tipping points, such as sensitivity to external forcing. To this end, we force the Community Ice Sheet Model v.2 (CISM2) by cycling different SMB climatologies previously calculated at multiple elevation classes with the Community Earth System Model v.2 (CESM2) in a two-way coupled CESM2–CISM2 transient simulation of the global climate and GrIS under high CO₂ forcing. The SMB calculation in CESM2 has been evaluated with contemporary observations and high-resolution modelling and includes an advanced representation of surface melt and snow–firn processes.

We find a positive SMB threshold for complete GrIS melt of 230 ± 84 Gt yr⁻¹, corresponding to a 60 % decrease in SMB and to a global mean warming of +3.4 K compared to pre-industrial CESM2–CISM2 simulated values. In our simulations, a small change in the initial SMB forcing (from 255 to 230 Gt yr⁻¹) and global mean warming above pre-industrial levels (from +3.2 to +3.4 K) causes an abrupt change in the GrIS final volume (from 50 % mass to nearly complete deglaciation). This nonlinear behaviour is caused by the SMB–elevation feedback, which responds to changes in surface topography due to surface melt and GIA. The GrIS tips from ∼ 50 % mass towards nearly complete melt when the impact of melt-induced surface lowering outweighs that of GIA-induced bedrock uplift and the (initially positive) SMB becomes and remains negative for at least a few thousand years. We also find that the GrIS tips towards nearly complete melt when the ice margin in the central west unpins from a coastal region with high topography and SMB. We show that if we keep the SMB fixed (i.e. no SMB–elevation feedback) in this relatively confined region, the ice sheet retreat is halted and nearly complete GrIS melt is prevented even though the initial SMB forcing is past the threshold. Based on the minimum GrIS configuration in previous paleo-ice-sheet modelling studies, we suggest that the surface topography in the central west might have played a role in preventing larger GrIS loss during the last interglacial period ∼ 130–115 kyr BP.

https://tc.copernicus.org/articles/19/63/2025/

At its core, the study uses computer models—specifically, the Community Ice Sheet Model (CISM2) coupled with the Community Earth System Model (CESM2)—to simulate the potential melting of the Greenland Ice Sheet (GrIS) under “high CO₂ forcing” conditions. The authors claim that a small shift in surface mass balance (SMB) can trigger “nearly complete deglaciation” of Greenland, a scenario that supposedly kicks in at a global mean warming of just +3.4°C above pre-industrial levels. They argue that the ice sheet is precariously balanced and susceptible to a so-called “tipping point,” where melt-induced surface lowering and glacial isostatic adjustment (GIA) would ensure its near-total collapse.

But here’s the problem: This scenario is entirely model-driven, with little to no real-world validation. And, more importantly, it hinges on assumptions that stretch the limits of scientific credibility.

Let’s first address the elephant in the room: The models. Climate models have long been notorious for over-predicting warming and ice loss. The CESM2 model used in this study is based on a set of emissions scenarios that often bear little resemblance to reality. Many climate fearmongers rely on Representative Concentration Pathway 8.5 (RCP8.5) or its newer equivalent, which assumes an implausible, nearly exponential rise in CO₂ emissions. The authors use the phrase “high CO₂ forcing” without specifying exactly which emissions scenario they are relying on, which is a red flag. If they are using a worst-case emissions scenario (which is common in these kinds of papers), then the entire study is essentially a speculative thought experiment rather than serious scientific inquiry.

Additionally, their model hinges on precise thresholds for ice sheet collapse, where a shift in SMB from 255 to 230 Gt/yr supposedly tips the entire Greenland Ice Sheet into a death spiral. This type of binary “all-or-nothing” thinking is a hallmark of alarmist climate science—where gradual, complex processes are reduced to dramatic tipping points that conveniently align with political talking points.

The timing of this paper is particularly interesting. With growing skepticism toward extreme climate policies, alarmist scientists and policymakers need fresh headlines to keep the public anxious. The message embedded in this study is clear: Act now or face an ice sheet apocalypse.

The funding mechanisms behind this research must also be scrutinized. Scientists who predict moderate, manageable climate outcomes rarely get their work amplified by the media or rewarded with large grants. But those who conjure up worst-case scenarios? They’re invited to speak at global summits, write op-eds in major newspapers, and shape government policy.

It’s a well-known trick: Use models to create a frightening future scenario, generate media buzz, and pressure policymakers into adopting economically disastrous “green” policies, all while ensuring the continued flow of research funding.

While Greenland has experienced ice loss in recent decades, its ice sheet is nowhere near a “tipping point.” Studies based on real-world observations—not just computer simulations—show that Greenland’s ice mass fluctuates naturally, with periods of melt and growth. During the Holocene Thermal Maximum (roughly 8,000 to 5,000 years ago), temperatures in Greenland were significantly warmer than today, yet the ice sheet remained intact.

Moreover, the study acknowledges that certain geographical features have historically prevented large-scale ice loss, such as the high topography in Greenland’s central west region. This means that even under extreme warming scenarios, a total collapse of the ice sheet is unlikely.

This paper is yet another example of how climate science has been hijacked by a political agenda. Instead of providing a balanced analysis of Greenland’s future, it cherry-picks an extreme scenario and markets it as inevitable. Worse still, it provides policymakers and activists with ammunition to justify economically crippling regulations based on speculative, unverifiable computer models.

The bottom line? The Greenland Ice Sheet is not on the brink of collapse, and no amount of fearmongering can change that. But as long as there’s funding and media attention to be gained from doomsday predictions, expect more of the same.

HT/Chris Martz