How do we know that the current climate change is not the same as the ‘medieval warm period’?

How do we know that the current climate change is not the same as the ‘medieval warm period’?

On ‘La noche de Dieter’, a radio programme moderated by Dieter Brandau on esRadio, claims were made that relativised the impact of the current climate change, stating that the present situation was comparable with the medieval warm period, a period of abnormally high temperatures that occurred in the Northern Hemisphere between the years 950 and 1250. Their analysis is MISLEADING.

While it is true that there have been periods in which temperatures were higher than normal, the current climate change is not comparable to the medieval warm period because the temperature increases have different causes. What’s more, the current climate change is global, while the medieval warm period was only recorded in the Northern Hemisphere and the current temperatures are the highest on record in Europe in 1,400 years.

When they say how lucky the people in the Middle Ages were because there was a medieval warm period, well, hey, maybe now we’re having a contemporary warm period.

The medieval warm period, also known as the medieval climate optimum or the medieval climatic anomaly, lasted from approximately 950 to 1250, during part of the Middle Ages in Europe. During this period, temperatures rose noticeably in the Northern Hemisphere, especially in numerous North Atlantic regions and Europe, with values that were higher than on the rest of the planet.

Some sceptics have used the fact that this warm episode occurred as an argument to suggest that the present climate change could be a repeat of this other episode. However, the comparison is misleading because they were not caused by the same thing, the level of temperatures reached both times was not the same, and the area of influence in each episode was not the same, either.

Unlike the medieval warm period which resolved itself naturally – in 1250, a period known as the Little Ice Age began – the current-day climatic change will only be mitigated by reducing greenhouse gas emissions.

Sunlight was to blame

The current climate change is caused by excess carbon dioxide emissions that result from the burning of fossil fuels, such as natural gas, petroleum or carbon, as we previously explained.

The medieval warm period occurred, according to various studies, in conjunction with two events that contributed to increased air temperatures: an increase in solar radiation and the absence of volcanic activity. In addition to those two factors, scientists have suggested in various papers, such as this one in Science, that there were also changes in ocean circulation patterns during this period, which brought warmer seawater to the North Atlantic.

The highest temperatures in 1,400 years

Although average temperatures during the Middle Ages may have been higher than those that occur now in some regions locally, it is not the case globally. This was proven by a multidisciplinary paper published in 2013 by Nature Geosciences in which almost 80 scientists discovered that temperatures are higher today than at any other time in the past 1,400 years, including during the medieval warm period.

The Intergovernmental Panel on Climate Change – a.k.a. the IPCC, the UN’s scientific body that systematically reviews and puts together reports on the current state of knowledge on climate change – noted as early as its fourth report, published in 2007, that during the medieval warm period, the temperatures “were probably 1.0°C to 2.0°C above early 20th-century levels at various European locations”.

“To put it in context, it is estimated that since the middle of the 19th century the average temperature in Europe as a whole has risen by more than 2ºC”, Rubén del Campo, meteorologist and spokesperson of Spain’s State Meteorological Agency (AEMET), tells Verificat.

A centuries-long ‘summer’… in the Northern Hemisphere

Lastly, the influence of the medieval warm period was confined solely to the Northern Hemisphere, as has been shown by several studies and analyses published in journals such as Science Advances.

In a more recent publication of Nature, other researchers stated that “the warmest period of the past two millennia occurred during the 20th century for more than 98% of the globe”, which provides “strong evidence that anthropogenic global warming is not only unparalleled in terms of absolute temperatures, but also unprecedented in spatial consistency within the context of the past 2,000 years”.

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