Roman Warm Period Was 2°C Warmer Than Today, New Study Shows

The Mediterranean Sea was 3.6°F (2°C) hotter during the Roman Empire than other average temperatures at the time, a new study claims.

Comparison of the records from Sicily Channel studied in this work (thick dark blue line) in comparison with other samples – Alboran Sea (thick light blue line), Minorca Basin (thick red line) and Aegean Sea (thick dark and light green lines). They support the claim that the Roman Period saw a 3.6°F  rise in temperatures in the Med

The study identifies the Roman period (1-500 AC) as the warmest period of the last 2,000 years. Map A shows the central-western Mediterranean Sea. Red triangle shows the location of the sample studied, while the red circles are previously-found marine records used for the comparison. Map B shows the Sicily Channel featuring surface oceanographic circulation and sample location. Black lines follow the path of surface water circulation

Spanish and Italian researchers recorded ratios of magnesium to calcite taken from amoebas present in marine sediments, an indicator of sea water temperatures. The skeletonised G. ruber was sampled from a depth of 1,500 feet (475m) located in the northwestern part of the Sicily Channel

For the first time, we can state the Roman period was the warmest period of time of the last 2,000 years, and these conditions lasted for 500 years,’ said Professor Isabel Cacho at the Department of Earth and Ocean Dynamics, University of Barcelona.

The Mediterranean is a semi-closed sea, meaning it is surrounded by land and almost only connected to oceans by a narrow outlet, and is a climate change ‘hot spot’ according to a previous paper. 

Situated between North Africa and European climates, the sea occupies a ‘transitional zone’, combining the arid zone of the subtropical high and humid northwesterly air flows.

This makes it extremely vulnerable to modern and past climate changes, such as changes in precipitation change and average surface air temperature, and is of ‘particular interest’ to researchers. 

Home to many civilisations over the years, the Med, or Mare Nostrum as it was known by ancient Roman civilisations, has become a model to study the periods of climate variation.

Reconstructing previous millennia of sea surface temperatures and how it evolved is challenging, due to the difficulty retrieving good resolution marine records.

However, the study of the fossil archives remains the only valid tool to reconstruct past environmental and climatic changes as far back as 2,000 years ago, they say. 

Compared to the subsequent period of the Roman Empire, the Mediterranean was characterised by a colder phase from around 500 BC to 200 BC. 

This corresponds with the beginning of the so-called ‘sub-Atlantic phase’ characterised by a cool climate and rainy winters which was favourable for Greek and Roman civilisations to grow crops. 

The cool and humid climate of the sub-Atlantic phase lasted until around 100 BC and covered the entire period of the monarchy in Rome. 

However, in 400 BC, cultural changes were synchronised across the Mediterranean region and more ‘homogeneous’ temperature conditions across the Med regions were established.

A distinct warming phase, running from AD 1 to AD 500, then coincided with the Roman Period and covered the whole Roman Empire archaeological period. 

‘This pronounced warming during the Roman Period is almost consistent with other marine records from Atlantic Ocean,’ the team say in their research paper, published in Scientific Reports.  



This climate phase corresponds to what is known as the ‘Roman Climatic Optimum’ characterised by prosperity and expansion of the Empire, giving warmth and sunlight to crops. 

Roman Climatic Optimum, a phase of warm stable temperatures across much of the Mediterranean heartland, covers the whole phase of origin and expansion of the Roman Empire. 

The greatest time of the Roman Empire coincided with the warmest period of the last 2,000 years in the Mediterranean. 

After the Roman Period, a general cooling trend developed in the region with several minor oscillations in temperature. 

The climate then transitioned from wet to arid conditions and this could have marked the decline of the golden period of the Roman Empire after AD 500.  

These new record correlated with data from other areas of the Mediterranean – the Alboran Sea, Menorca basin and Aegean Sea. 

‘We hypothesise the potential link between this Roman Climatic Optimum and the expansion and subsequent decline of the Roman Empire.’ 

The study provides high resolution and precision data on how the temperatures evolved over the last 2,000 years in the Mediterranean area.  

It also identifies a warming phase that’s different during the Roman Empire in the Mediterranean area and is focused on the reconstruction of the sea surface temperature over the last 5,000 years. 

‘Our study highlights the relevance of the Roman Empire to better understand the behaviour of the Mediterranean climate – specifically, the hydrological cycle – in warm conditions compared to the ones in the current climate change scene,’ said Professor Cacho.

‘This part of the research is essential to improve our ability to adapt to imminent changes.’

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