Global average surface temperature: the measurements from 1850 until the present indicate that Planet Earth is increasingly warm | Photo: Gomes/Creative Commons

The records of global surface temperature started in 1850. Since then, Humanity has been able to register, analyze, and compare the evolution and shifts in warmth and coolness throughout the world.

Over the past century and a half, the planet has experienced a remarkable shift in temperature, primarily driven by human activities.

Despite the vast fluctuations across different regions and seasons, scientists have developed methods to calculate a global average temperature.

Calculation involves gathering temperature data from various monitoring stations worldwide.

However, simply averaging these absolute readings wouldn't accurately represent temperature changes over time due to factors like seasonal variations, local climate differences, and instrumental biases.

To address this, scientists employ a method known as temperature anomalies.

Deforestation: forest loss and damage is the cause of around 10 percent of global warming | Photo: Palmer

What Is a Temperature Anomaly?

The concept of temperature anomaly is fundamental in understanding climate data analysis.

It refers to the deviation or departure of a measured temperature from a specified reference value or long-term average.

This reference value could be the average temperature for a specific location and time period, often calculated over several decades to establish a reliable baseline.

When a temperature anomaly is positive, it signifies that the observed temperature was warmer than the reference value or long-term average. 

In other words, the actual temperature was higher than what would typically be expected for that particular time and place.

Positive anomalies indicate periods of above-average warmth relative to the historical norm.

Conversely, a negative temperature anomaly indicates that the observed temperature was cooler than the reference value or long-term average.

In this scenario, the actual temperature was lower than what is considered typical for the given location and time frame.

Negative anomalies represent periods of below-average temperatures compared to historical norms.

So, instead of focusing on absolute temperature values, scientists compare each recorded temperature with the long-term average temperature for that specific location and date.

This comparison yields a temperature anomaly, representing how much warmer or cooler the observed temperature is compared to what's typical for that particular time and place.

By using temperature anomalies, scientists can effectively filter out short-term fluctuations and isolate long-term trends in temperature data.

This approach helps to track changes in temperature more accurately, allowing for a clearer understanding of global climate patterns and trends over time.

Glaciers: between 2002 and 2023, Antarctica shed an average of 150 billion metric tons of ice per year, adding to global sea level rise | Photo: Desgagnes/Creative Commons

Why 2023 Matters

The year 2023 marked a significant milestone in our climate records.

According to the 2023 Global Climate Report by NOAA National Centers for Environmental Information, every month of the year ranked among the warmest on record, with the latter half of the year witnessing unprecedented warmth.

July, August, and September each surpassed the threshold of 1.8 °F ( 1.0 °C) above the long-term average, setting alarming precedents.

The record warmth extended beyond individual months, with 2023 being declared the warmest year on record for both land and ocean areas, individually and combined, across both the Northern and Southern Hemispheres.

Furthermore, while Antarctica experienced its 40th-warmest year, the Arctic faced its fourth-warmest year, indicative of the disproportionate impact of climate change on polar regions.

Understanding the Past to Act Now and Save the Future

The upward trajectory of global temperatures highlights the pervasive influence of human activities, particularly greenhouse gas emissions.

Since 1850, the combined land and ocean temperature has risen at an average rate of 0.11 °F (0.06 °C) per decade, with a threefold acceleration since 1982.

The scientific consensus, as articulated by the Intergovernmental Panel on Climate Change (IPCC), leaves no doubt regarding the anthropogenic origins of this warming trend.

Looking ahead, the amount of future warming hinges on our collective response to emissions.

Current trends suggest a continuation of temperature increases, with models projecting a range of scenarios based on different emission trajectories.

Without substantial reductions in greenhouse gas emissions, the Earth faces the prospect of temperature increases ranging from 2.4 °F to over 10 °F by the end of the century, with profound implications for ecosystems, economies, and human well-being.

In the face of these projections, understanding the evolution of global temperatures is paramount.

The Evolution of Global Average Surface Temperature

The world temperature evolution graph above showcases the progress of the Blue Planet's average surface temperature from year 1,850 up to today.

It is based on NASA's Land-Ocean Temperature Index, a tool used to track the changes in global average temperatures over extended periods.

It calculates temperature anomalies, which indicate how much warmer or cooler a specific year is compared to the average temperature over a 30-year period.

This index utilizes data from weather stations to monitor land temperatures and incorporates temperature reports from ships and buoys to account for ocean temperatures.

By combining both land and ocean data, it provides a comprehensive understanding of global temperature trends over time.

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The records of global surface temperature started in 1850. Since then, Humanity has been able to register, analyze, and compare the evolution and shifts in warmth and coolness throughout the world.