May 2024 was the warmest May on record, confirming the year-to-date’s track record of record high temperatures, according to NASA.

Average global temperatures over the past 12 months reached record highs for each corresponding month, which scientists from the NASA’s Goddard Institute for Space Studies (GISS). in New York they call it unprecedented.

The run of record temperatures is part of a long-term warming trend attributed to human activity, mainly greenhouse gas emissions. The trend has been evident over the past four decades, with the past 10 consecutive years being the warmest since record-keeping began in the late 19th century. Before this streak of 12 consecutive months of record temperatures, the second-longest streak spanned seven months between 2015 and 2016.

In NASA’s analysis, a temperature base value is defined by several decades or more, usually measuring 30 years. The average global temperature over the last 12 months was 1.30 degrees Celsius above the 20th century baseline; in the period 1951 to 1980. The measurement is slightly above 1.5 degrees Celsius, the late 19th century average.

To calculate Earth’s global temperature, NASA scientists collect data from tens of thousands of weather stations on land and from thousands of instruments placed on ships and buoys on the ocean surface. This raw data is analyzed using methods that take into account the varying spacing of temperature stations around the world.

El Niño is fading, La Niña is coming

Phenomena such as El Niño and La Niña, which alternately warm and cool the tropical Pacific Ocean, can contribute to little variability in global temperatures from year to year. The strong El Niño that began in the spring of 2023 helped trigger last year’s extreme summer and fall heat.

As of May 2024, scientists at NOAA’s (National Oceanic and Atmospheric Administration) Climate Prediction Center predicted a 49% chance of La Niña occurring between June and August and a 69% chance between July and September. The La Niña phenomenon could partially suppress average global temperatures this year.

It is hard to know whether 2024 will set another global heat record. Factors such as volcanic eruptions and aerosol emissions can affect the climate each year.

Ocean temperatures and hurricanes

Scientists are watching to see how ocean temperatures might affect this year’s hurricane season. Temperatures remained warm as the 2024 hurricane seasons began. Across the Northern Hemisphere, ocean temperatures for the January-April period were 1.18 degrees Celsius above average, according to NOAA. Despite the waning of El Niño, sea surface and deeper temperatures are still above average in many places, said Josh Willis, an oceanographer at NASA’s Jet Propulsion Laboratory in Southern California.

NASA researchers report that increasing carbon dioxide emissions are the main cause of ocean warming. Up to 90% of excess atmospheric heat in recent decades has been absorbed by the ocean, with much of this heat being stored near the water’s surface.

La Niña years can also contribute to more active Atlantic hurricane seasons. This is because the conditions created by La Niña weaken the westerly winds high in the atmosphere near the Americas, over the Caribbean Sea and the tropical Atlantic Ocean. Wind shear, sudden changes in its speed and direction, can slow down hurricanes before they develop.