1.5 degrees Celsius has become a symbol of global climate change negotiations.
Countries have agreed to "continue efforts" to limit global temperature rises to 1.5 degrees Celsius under the 2015 Paris agreement.
The overheated world will likely exceed a significant temperature limit for the first time in the next few years, according to information quoted by the BBC.
Scientists say there is a 66% chance of crossing the 1.5C global warming threshold between now and 2027.
The chances are increasing due to emissions from human activities and the anticipated "El Nino" weather event this summer.
While scientists think that this violation will be temporary, they emphasize their concerns.
Reaching the threshold means the world is 1.5 degrees Celsius warmer than it was in the second half of the 19th century, when fossil fuel emissions from industrialization really started to increase.
Going above 1.5 degrees Celsius each year for ten or twenty years will cause far greater warming effects, such as longer heatwaves, more intense storms and wildfires.
"El Nino" refers to the unusual warming of surface waters in the eastern tropical Pacific Ocean.
Occurring irregularly at intervals of 2 to 7 years, El Nino has an impact on ocean temperatures, the speed and strength of ocean currents, and local weather.
"La Nina" is used as a model to describe the unusual cooling of the region's surface waters.