A groundbreaking study using the PhanDA model offers a new view of Earth’s temperature over the last 485 million years, showing a dynamic range of climates significantly influenced by CO2 levels.
The analysis identifies five distinct climate states, suggesting a predominant history of warmer temperatures, which underscores the complex relationship between atmospheric CO2 and long-term climate variability.
Understanding Earth’s Climate Through Time
Estimating past global temperature is important for understanding the history of life on Earth and for predicting future climate. Now, a new reconstruction of Earth’s temperature history over the past 485 million years – based on a method that combines diverse physical proxy data with climate model predictions – reveals a much wider range of climate variability across the Phanerozoic eon than previously understood.
The findings highlight atmospheric carbon dioxide (CO2) as the dominant factor controlling climate variability throughout this period, offering new insights into the Earth’s climate sensitivity across long timescales.
Phanerozoic Climate Insights
A record of global mean surface temperature (GMST) throughout the Phanerozoic – the last 540 million years during which animals and plants evolved – is crucial. Over the last 500 million years, climate shifts across the Phanerozoic have been closely tied to biological evolution, tectonic activity, and atmospheric and ocean chemistry. Studying this temperature evolution helps clarify the mechanisms driving long-term climate changes.
Additionally, GMST data from the Phanerozoic provides important context for current human-induced warming. However, temperature reconstructions from this period have traditionally relied on disparate, incomplete proxy data or predictions from Earth systems models, which are difficult to confirm.
According to Emily Judd and colleagues, both methods have suggested that global Phanerozoic temperatures have been generally colder and less variable than other studies of recent geological periods have shown. Such discrepancies raise doubts about the current view of Earth’s long-term climatic history.
Introducing PhanDA: A New Temperature Model
Judd and colleagues present PhanDA – a state-of-the-art reconstruction of GMST spanning the last 485 million years. PhanDA is based on paleoclimate data assimilation (DA), a technique that statistically blends geological proxy data on past conditions with Earth system model simulations to create a more complete record of surface air temperatures across the Phanerozoic.
According to Judd et al., the PhanDA reconstruction reveals that Earth’s temperature has varied more dynamically than previously thought, exhibiting a large range of GMST, spanning 11 degrees Celsius (°C) to 36° C.
Implications of the PhanDA Study
The authors also identified five distinct climate states and show that more of Earth’s history was spent in warmer rather than colder climates. Moreover, the findings demonstrate a strong link between global temperatures and atmospheric carbon dioxide levels, suggesting that CO2 has been the primary driver of climate changes over this period.
However, Judd et al. note that the nature of this link is likely complex and will require further research to constrain. In a Perspective, Benjamin Mills discusses the study and its limitations in greater detail.
Reference: “A 485-million-year history of Earth’s surface temperature” by Emily J. Judd, Jessica E. Tierney, Daniel J. Lunt, Isabel P. Montañez, Brian T. Huber, Scott L. Wing and Paul J. Valdes, 20 September 2024, Science.
DOI: 10.1126/science.adk3705
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5 Comments
“The findings highlight atmospheric carbon dioxide (CO2) as the dominant factor controlling climate variability throughout this period, offering new insights into the Earth’s climate sensitivity across long timescales.”
Strangely, they don’t mention what they assume that climate sensitivity is for a doubling of CO2, despite claiming that CO2 is the “dominant factor.” They also don’t mention the lapse rate. This is important because temperature varies significantly with elevation and one has to know quite a bit about the topography to dismiss it as not being a significant factor, especially during orogenies, or mountain building episodes, when mountains were often higher than they are today, except maybe in the Himalayas. Because CO2 is acknowledged to be well-mixed, the elevation of land cannot be ignored. There is a problem in that as the mountains are eroded, little is left that can be used as terrestrial temperature proxies, except in lowland swamps. It would seem then that there would be a bias for higher temperatures from terrestrial rocks.
“Moreover, the findings demonstrate a strong link between global temperatures and atmospheric carbon dioxide levels, suggesting that CO2 has been the primary driver of climate changes over this period.”
“Correlation does not establish causation” is a truism that is often ignored. It is evident that, today, seasonal CO2 variations are driven by biology, particularly in the northern hemisphere. (CO2 builds up from Fall of one year to May of the following year, from decomposition of dead phytoplankton and leaf litter, and respiration of dormant trees; the atmospheric CO2 peaks in May, when trees start to leaf out, and declines rapidly until Fall.) Furthermore, during warm El Nino years, the Winter ramp-up of CO2 is steeper and has a greater range than other years, making it appear that temperature is driving CO2, not the other way around. Lastly, during the COVID shutdowns, despite anthropogenic CO2 declines of about 6-10% for the year, and the month of April alone being about 14-18% less than the previous year’s anthropogenic emissions, the seasonal CO2 ramp-up graph is indistinguishable from the preceding or subsequent years. Then there are the Law Dome ice cores (Antarctica) that suggest that CO2 follows temperature changes.
While there are good scientific reasons for believing that CO2 drives temperatures, the empirical support is not as strong as many claim. It would appear that there are feedback loops that moderate the theoretical impact. Claims that CO2 is the “dominant factor” in Earth temperatures is poorly supported, despite what most researchers claim.
Based on proxy (substitute assumed data) and climate change models. When we can’t even get a reliable 3-5 day weather forecast out a computer simulation, we’re supposed to trust a highly politicized climate change simulator for over 400 MILLION YEARS!?! Lol. Yeah, okay.
Ironically, it says the earth has been warmer not colder for much of that time andife thrived on Earth. We’ve been warming since the relatively sudden (likely meteorite driven) ice age ended (known as Ragnarock in Nordic myth and a massive Flood in more religious accounts). Whether industrialization is fully or partly to blame for the past 40 years (we seemed to be trending in the other direction for a couple of decades in the 60s and 70s, long after most US industrialization started and ironically the USA has the most stable temperatures on the planet, barely changing compared to the rest of the world.
Northeast Ohio’s weather has never even gone over 100F since the 1980s despite all the talk of obscene temperature extremes. It went over twice on the 80s when then “global warming” was barely mentioned and far from settled. Now if you so much as disagree in the field, you lose your job! That’s how open minded these so-called “scientists” are. They’re more like little bullies on the playground.)
Yeh…what Clyde Spencer said.
As there have been 5 ice ages where the earths temperature has varied by as much as 10 to 11 degrees Celsius ( from very warm to very cold) BEFORE man even existed, how are scientist so certain as to how much mans existence even matters to changing temperatures today? The earth is 4 BILLION years old and these 5 ice ages started and then gradually declined over 10’s if not 100’s of millions of years.
Ice ages? Uniformitarian ancient age thinkers ignore a world wide flood necessitating only one ice age…and of short duration.