Pictured is a graph of historical global sea-surface temperatures across the year from 1982-2024. Yesterday was about 0.3°C warmer than last year. Well, maybe it will go back down since this is an El Niño year? :>
Average global surface air temperature in February 2024 was 1.77°C warmer than the average February from 1850-1900. So maybe we can retire those 1.5°C warming goals now?
However, the IPCC reports that global temperatures have only risen by 1.1°C. This is because they use decade-long averages. Indeed, it is completely possible that 2025 will be cooler than 2024, but crop failures don't care much for averages. 
And if global warming has accelerated, the IPCC's method will be a decade late to realizing it. Not that they can actually do anything about it...
Just a guess, but the earth orbits closer to the sun during the northern hemisphere’s summer and farther during the northern hemisphere’s winter.
There's also not the same amount of ocean surface on the northern hemisphere and southern hemisphere, although I think this actually cancels out some of the difference due to Earth's orbit.
Ocean currents are pretty significant as well - if Antarctica wasn't surrounded by huge oceans on all sides we probably wouldn't have any icecaps left already
Yeah, the other comment explained the actual reason, which is ocean currents. I was just spitballing but both the reasons in this particular thread of responses are extremely small next to ocean currents.