Global Warming Timeline Moved Up, New Study Claims

It’s impossible to have missed the near-ubiquitous call to action to “keep temperatures from exceeding 1.5 degrees Celsius compared to pre-industrial levels” over the past few years. The somewhat bureaucratic phrase has become a rallying cry for the climate-conscious, first appearing after the landmark Paris Climate Agreement in 2015.

This ambitious target describes a climate threshold-if we pass and maintain a long-term average global temperature increase of 1.5 degrees Celsius for several years. Well, a new study from the University Western Australia Oceans Institute published in Nature Climate Change has some bad news: we might have already blown past that crucial 1.5 degree Celsius threshold in 2020, a full four years ago.

New Study Claims We Surpassed 1.5 Celsius Global Warming Years Ago

According to a recent study from the University Western Australia Oceans Institute, the world may have surpassed the ambitious 1.5 celsius global warming threshold set by the Paris Climate Agreement several years ago. The study analyzed six Caribbean sclerosponges, a type of sea sponge, to create an ocean temperature timeline dating back to 1700.

By measuring strontium-to-calcium ratios in the sponges, researchers calculated that ocean temperatures in the region have risen by more than 1.7 celsius since pre-industrial times. If accurate, this means we blew past the 1.5 celsius mark around 2020, nearly half a decade ago.

It Is Not All Set In Stone

However, some scientists remain skeptical that data from a single region can capture the immense complexity of global ocean temperatures. An expert speaking with LiveScience said, “It begs credulity to claim that the instrumental record is wrong based on paleosponges from one region of the world…It honestly doesn’t make any sense to me.”

Regardless of the study’s accuracy, there are signs we’re rapidly approaching the 1.5 celsius threshold. This January was the hottest, measuring 1.7 celsius above pre-industrial temperatures. According to New Scientist, staying at this level for an extended period means we’ve likely surpassed 1.5 celsius of warming for at least a year.

Analyzing Ancient Caribbean Sponges to Create a Climate Timeline

By examining strontium-to-calcium ratios in these sponges, the researchers calculated sea surface temperatures over the last 300 years. The sponges’ location in the Caribbean Sea is ideal for this type of research because major ocean currents do not distort temperature readings.

The sponge study provides an intriguing new window into historical sea temperatures but requires validation from additional research. While it suggests the climate change timeline may need to be accelerated, overturning the current scientific consensus will require extensive review and discussion among experts in the field.

Sponges Act as “Natural Archives” Locking Away Centuries of Climate Data

A new study from the University Western Australia Oceans Institute analyzed six sclerosponges, a type of sea sponge that clings to underwater caves, to unlock a climate record dating back to 1700. These sponges are ideal for studying past climate conditions because they grow at an incredibly slow rate-just a tiny fraction of a millimeter per year.

This slow growth allows the sponges to capture clues about the ocean environment and lock them away in their limestone skeletons, similar to how tree rings or ice cores provide a window into the past. By measuring the ratios of strontium to calcium in the sponges, the researchers were able to calculate sea surface temperatures over the last 300 years.

Strontium to Calcium Ratios Allow Researchers to Calculate Historic Ocean Temps

By measuring strontium-to-calcium ratios in the sponges’ limestone skeletons, scientists were able to calculate ocean temperatures dating back to 1700. Since these sponges reside in the Caribbean, major ocean currents don’t impact temperature readings.

While controversial, the study is a reminder that climate change is an urgent problem. As lead author Malcolm McCulloch told the Associated Press, “The big picture is that the global warming clock for emissions reductions to minimize the risk of dangerous climate change has been brought forward by at least a decade. Basically, time’s running out.”

Some Scientists Question Basing Global Climate on One Region’s Data

While the sponges’ location in the Caribbean is advantageous due to minimal interference from ocean currents, the region’s temperatures may not accurately reflect the overall global climate and complex thermal variations of the world’s vast seas.

Proponents counter that the study’s 80-year acceleration of global warming corresponds with human activity and fossil fuel usage, providing further evidence that human-caused climate change is an urgent problem requiring immediate action.

What Do These Findings Mean for the Paris Climate Agreement Goals?

The study’s conclusions pose some serious questions about the goals laid out in the Paris Climate Agreement. The agreement set the ambitious target of limiting global warming to 1.5 celsius to avoid catastrophic damage. If accurate, this means the world is already grappling with more severe climate change effects than expected this early on.

If the sponge study is correct, it paints a sobering picture of our progress (or lack thereof) in mitigating climate change. The 1.5 celsius threshold was designed to minimize catastrophic damage, but we may have surpassed it without realizing it.

How Reliable Are Historic Ocean Temperature Measurements?

Sclerosponges are useful for studying past climate conditions because they grow at an incredibly slow and steady rate, depositing a new limestone layer each year that records the temperature and chemistry of the surrounding seawater.

The location of these sponges in the Caribbean also provides reliable data free of disturbances from major ocean currents. Still, as valuable as these natural archives may be, they represent temperatures for only a small portion of the global ocean. The study’s conclusions seem to contradict direct instrumental measurements showing roughly 1.2 celsius of warming so far.

Facing The Reality

The Intergovernmental Panel on Climate Change (IPCC) also uses a baseline of 1850 to 1900, rather than the 1700s, to determine pre-industrial temperatures. Considering the immense complexity of mapping global temperatures, more data may be needed before significantly revising established models and goals.

Sea sponges and other natural proxies can provide a long view of ocean conditions, but interpreting what they reveal may prove as tricky as finding consensus on solutions to this urgent problem. The truth likely lies somewhere in between the worrying conclusions of this study and skepticism from the scientific community-a call for action but also a caution against overreaction before the evidence is in.

What Can Be Done?

Whatever your stance on climate change, it’s impossible to have missed the near-ubiquitous call to action to “keep temperatures from exceeding 1.5 degrees Celsius compared to pre-industrial levels.” The 1.5-degree threshold has become a rallying cry for the climate-conscious.

While concerning, basing such a conclusion on a small dataset from one region seems premature. More comprehensive global data is needed. Still, as the study’s lead author said, “Basically, time’s running out.” The takeaway seems clear: we need accelerated action on emissions reductions worldwide if we hope to avoid the most dangerous climate change scenarios.