The surface temperature of the world's oceans reached new record levels in the first months of 2024, continuing the trend started in April 2023. As of August 6, 2024, the global sea surface temperature reached 20.98 degrees Celsius, an increase of 0.76 degrees compared to the 1982-2010 average. Overall, 2024 was a year of record temperatures on land and in the sea, with a temperature anomaly of 1.29 degrees with respect to the 20th century average. As of May 2025, temperatures this year remain lower than 2024 temperatures.

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The C3S global Sea Surface and Sea Ice Temperature Reprocessed product provides gap-free maps of daily average SST at 20 cm depth and IST skin at 0.05deg. x 0.05deg. horizontal grid resolution, using satellite data from the ESA SST_cci v3.0 L3U data from (A)ATSRs, SLSTR and AVHRR, L2P data from the AMSRE and AMSR2 Passive Microwave Instruments (Embury et al., 2024) and L2P data from the AASTI and C3S IST CDR/ICDR v.1. The C3S level 4 SST/IST analyses were produced by running the DMI Optimal Interpolation (DMIOI) system (Høyer and She, 2007; Høyer et al., 2014; Nielsen-Englyst et al., 2023, Nielsen-Englyst et al., 2024) to provide a high resolution (1/20deg. - approx. 5km grid resolution) daily analysis of the daily average sea surface temperature (SST) at 20 cm depth and sea ice surface temperature (IST) at the surface skin to cover surface temperatures in the global ocean, the sea ice and the marginal ice zone. It uses a Multi-Source Composite Sea-Ice concentration dataset (from a combination of EUMETSAT OSI-SAF OSI-450a (Lavergne et al., 2019), OSI-458, ESA CCI Sea ice CDR, SICCI-HR-SIC, U.S. National Ice Centre’s (NIC) ice charts, Swedish Meteorological and Hydrological Institute (SHMI) and Finnish Meteorological Institute’s (FMI) ice charts used for the Baltic region) developed at DMI for the purpose of the CARRA2 project (Pan-Arctic) and extended to the South Hemisphere.

'''DOI (product) :'''
https://doi.org/10.48670/moi-00169

The world's oceans are becoming increasingly acidic, with the average ocean pH falling from 8.11 in 1985 to 8.05 in 2022. This seemingly small change represents a significant increase in acidity, damaging the fine chemical balance of the oceans and posing a risk to marine ecosystems. The more emissions, the more acidic As global CO2 emissions continue to rise, the oceans absorb more CO2 per year, playing a crucial role in regulating atmospheric CO2 levels. The increased dissolution of CO2 in seawater causes the oceans’ pH to decrease. The acidification of the oceans creates conditions that dissolve minerals such as carbonates, which are the backbone of reefs and marine life’s shells and skeletons. In addition, certain species of harmful algae proliferate in acidified waters, putting fish, marine mammals, and the full food chain in danger. Warmer oceans on top of acidification Acidification is not the only climate change-related issue the oceans must adapt to. In 2023, the average ocean surface temperature worldwide was almost one degree Celsius higher than the 20th century average. Such departures from average conditions are called anomalies, and although they fluctuate, the global ocean surface temperature anomaly has shown a marked upward trend over the past decades. A warming ocean brings a series of cascading effects, including the melting of sea ice, sea level rise, and marine heatwaves. On top of that, less carbon sinks to the deep ocean in warmer waters, making them a less efficient carbon pool and therefore aggravating climate change.

ERA5 is the fifth generation ECMWF reanalysis for the global climate and weather for the past 8 decades. Data is available from 1940 onwards. ERA5 replaces the ERA-Interim reanalysis. Reanalysis combines model data with observations from across the world into a globally complete and consistent dataset using the laws of physics. This principle, called data assimilation, is based on the method used by numerical weather prediction centres, where every so many hours (12 hours at ECMWF) a previous forecast is combined with newly available observations in an optimal way to produce a new best estimate of the state of the atmosphere, called analysis, from which an updated, improved forecast is issued. Reanalysis works in the same way, but at reduced resolution to allow for the provision of a dataset spanning back several decades. Reanalysis does not have the constraint of issuing timely forecasts, so there is more time to collect observations, and when going further back in time, to allow for the ingestion of improved versions of the original observations, which all benefit the quality of the reanalysis product. ERA5 provides hourly estimates for a large number of atmospheric, ocean-wave and land-surface quantities. An uncertainty estimate is sampled by an underlying 10-member ensemble at three-hourly intervals. Ensemble mean and spread have been pre-computed for convenience. Such uncertainty estimates are closely related to the information content of the available observing system which has evolved considerably over time. They also indicate flow-dependent sensitive areas. To facilitate many climate applications, monthly-mean averages have been pre-calculated too, though monthly means are not available for the ensemble mean and spread. ERA5 is updated daily with a latency of about 5 days. In case that serious flaws are detected in this early release (called ERA5T), this data could be different from the final release 2 to 3 months later. In case that this occurs users are notified. The data set presented here is a regridded subset of the full ERA5 data set on native resolution. It is online on spinning disk, which should ensure fast and easy access. It should satisfy the requirements for most common applications. An overview of all ERA5 datasets can be found in this article. Information on access to ERA5 data on native resolution is provided in these guidelines. Data has been regridded to a regular lat-lon grid of 0.25 degrees for the reanalysis and 0.5 degrees for the uncertainty estimate (0.5 and 1 degree respectively for ocean waves). There are four main sub sets: hourly and monthly products, both on pressure levels (upper air fields) and single levels (atmospheric, ocean-wave and land surface quantities). The present entry is "ERA5 hourly data on single levels from 1940 to present".

land and oceanic climate variables. The data cover the Earth on a 31km grid and resolve the atmosphere using 137 levels from the surface up to a height of 80km. ERA5 includes information about uncertainties for all variables at reduced spatial and temporal resolutions.

In 2024, the average air temperature in Japan's capital reached around **** degrees Celsius. Tokyo's annual mean air temperature increased by **** degrees Celsius since 1900, showing the progress of global warming. Weather in Tokyo Tokyo lies in the humid subtropical climate zone. It is affected by the monsoon circulation and has mild, sunny winters and hot, humid, and rainy summers. In most of Japan, the rainy season lasts from early June to mid-July. Furthermore, heavy rainfall is often caused by typhoons, which develop over the Pacific Ocean and regularly approach the archipelago between July and October. In recent years, the Kanto region, including Tokyo Prefecture, was approached by at least two typhoons each year. Since the winters are rather mild in Tokyo, the capital city does not often see snowfall and the snow rarely remains on the ground for more than a few days. Effects of global warming in Japan The increasing air temperature is one of the main consequences of global warming. Other effects are increased flooding frequency and a rise in sea levels due to melting ice caps. Global warming has already influenced Japan's climate in recent years, resulting in more frequent heat waves as well as increased annual rainfall. These weather changes can intensify natural disasters such as typhoons and inhibit the growth of crops. To counter global warming, Japan aims to reduce its greenhouse gas emissions by increasing its renewable and nuclear energy share.