17.18C, and what it means

17.18 degrees Celsius (62.92F) is the warmest daily global temperature recorded since such records have been kept. It occurred Tuesday, July 4, 2023. The previous record (17.01) was set the prior day, and the most recent record before that was 16.92 set in August 2016. You may think that 63 degrees Fahrenheit doesn’t sound so hot. You would be wrong; consider that this is the average global temperature for the entire planet, including the coldest parts.

The highest annual temperature ever recorded occurred in 2020 when it tied 2016. Annual values consider the global values for the entire calendar year. Given the El Nino event that is currently underway, it is widely believed that 2023 and/or 2024 will surpass those previous records. The past eight years have been the warmest on record globally since records have been kept. The heat is fueled by ever-rising greenhouse gas concentrations and accumulated heat, according to six leading international temperature datasets consolidated by the World Meteorological Organization.

Even Climate Science’s most fervent deniers are now forced to admit that global warming is happening. Even so, some may question the time period. The climate is always changing, they posit, and the planet has been this hot at times in the past. Although true, this statement is misleading. Earth has not since we modern humans have been around.

Records have been kept for data such as that summarized here since around 1880. But accurate readings to measure the warmest daily global temperature have only been kept since 1979. How can we compare today’s temperatures to older data? This requires the use of indirect measurements and proxies, since systematic temperature records are only available for this relatively short period. Some of the methods used include the following:

- Historical documents, such as diaries, ship logs, and weather journals.
- Proxy Data: indirect evidence of past climate conditions that can be used to estimate temperature variations. Various natural proxies can provide information about past temperatures, such as tree rings, ice cores, corals, lake sediments, and stalagmites. These proxies contain climate-sensitive information that can be analyzed to reconstruct temperature patterns.
- Instrumental Data Overlap, where modern temperature records overlap with historical records or early instrumental measurements. These methods can help with calibration.
- Climate models (mathematical representations of the Earth's climate system).

By combining these methods, scientists can reconstruct past temperature patterns and make comparisons with present-day data. These comparisons provide insights into long-term climate trends and help understand how current temperature changes fit within the context of historical climate variations.

Therefore, when we state that the warmest days or the warmest years on record are occurring in recent decades, we can say with certainty that this can be verified over the past 140 years or so. But after examining all of the various measurement data, we can also say with reasonable confidence that the planet has not been this warm for well over 100,000 years. The last time the Earth experienced similar warmth was likely during the Eemian interglacial period, approximately 130,000 to 115,000 years ago. During that period, global temperatures were somewhat higher than today, and sea levels were higher as well.

To summarize the comparison of current temperatures to past temperatures, scientists have found that:

- The Earth is experiencing a period of rapid warming, and the last few decades have been among the warmest in thousands of years.
- The current rate of temperature increase is unprecedented in geological records, far exceeding natural variations that occurred over much longer timescales.
- The warming trend has been associated with more frequent and intense heatwaves, as well as changes in precipitation patterns and extreme weather events.
- The increase in global temperatures is attributed to human activities, particularly the emission of greenhouse gases, such as carbon dioxide, methane, and nitrous oxide, into the atmosphere.

It's crucial to keep in mind that comparing the current rate of warming to historical geological periods is not an exact analogy, as human civilization has developed during a relatively stable and cooler period in Earth's history. The rapidity of the ongoing changes and their potential impacts on ecosystems and human societies make them of great concern and underscores the importance of addressing climate change and its causes.

Climate change is happening in a big way, and this is only the beginning. We have the power to prevent it from getting much worse. All it will take is the will to do so. We’ve no time to lose.