A recent article in Reviews of Geophysics explores the characteristics and evolution of climate during the Late Pliocene and the Pliocene-Pleistocene transition, with the aim of identifying regions that may be vulnerable or resilient to future climate forces. Studying past climates is important because it allows us to understand when, how, and why climate change occurs. By examining past climates, we can investigate climate changes on a global, regional, and local scale, and gain a better understanding of the impacts of different causes, such as changes in greenhouse gases or variations in solar energy. It also allows us to identify parts of the climate system that are sensitive to change and regions or systems that are more resilient, such as oceans, ice sheets, and ecosystems.

The Pliocene, which occurred 2.7 to 5.3 million years ago, was characterized by a warmer climate than the preindustrial era. Global temperatures were 2-3 °C higher than preindustrial levels, with particularly high temperatures in polar regions and limited sea ice coverage. The Pliocene also saw smaller ice sheets in Antarctica and Greenland and a shift in vegetation zones towards the poles. Changes in oceanic gateways, such as the opening of the Panama Gateway and the closing of the Bering Strait, influenced oceanic circulation during this time.

Two important periods within the Pliocene are the mid-Piacenzian warm period (mPWP) and the intensification of Northern Hemisphere Glaciation (iNHG). The mPWP, which occurred around 3 million years ago, was a period of sustained warmth with atmospheric CO2 concentrations similar to current levels. After the mPWP, the climate began to cool, leading to the development and expansion of ice sheets in the northern hemisphere. This transition, known as iNHG, took place between 3 and 2.5 million years ago.

Understanding the transition from the Pliocene to the Pleistocene is crucial because it provides insights into the mechanisms driving large-scale climate transitions. By comparing the mean and amplitude of climate change during the mPWP and iNHG, researchers can identify the parts of the climate system that influenced stability and resilience, especially terrestrial ice sheets. This knowledge is valuable for predicting future climate scenarios, such as extensive melting of ice sheets due to global warming, and understanding the possible responses of oceanic and atmospheric circulation to these changes.

To answer questions about past climates, researchers rely on paleoclimatic proxies, which are indicators extracted from sediment samples from the seafloor. In this study, datasets of proxies for sea surface temperature and global ice volume were collected from sediment samples from the seafloor. Bayesian statistics-based algorithms were used to determine times of climate change, and comparisons with climate models were made.

In summary, studying past climates provides valuable information about future environmental responses and helps us prepare for possible climate changes. Understanding the characteristics and transitions of past climates allows us to identify vulnerable regions and systems and make informed predictions about future climate scenarios.