## 1 Introduction  
The impacts of anthropogenic climate change are becoming increasingly clear and tangible, affecting the bio-socio-economical fabric of all living organisms on our planet. The far-reaching implications of climate change mean that the need to assess the state of the climate becomes ever more important. What is the normal state of the climate? Which period can best represent the current state of the climate and be a reasonably good predictor for a near-future climate? Which basis shall be used for the near-real-time climate monitoring? Questions like these now have real, practical socio-economic implications. In light of these questions, the World Meteorological Organization (WMO) has provided guidelines to calculate the climate normals of geophysical variables in recent decades [1; 2; 3]. The WMO recommends that the member states shall update their climate normals every decade with the most recent 30-year period, finishing in a year ending with 0. This means that the latest 30-year normal period is considered to be 1991-2020. Previous studies have debated in detail whether these latest normals can really be representative of the current climate or be a predictor for a near future one, given the rapid and non-linear changes ongoing in the climate system [4; 5; 6; 7; 8; 9]. The economic implications of climate normals, for example in the energy sector, are also being discussed [10; 11]. Even the question of how to convey climate normals to the general public is far from straightforward [12; 13]. There are at least two important aspects that are worth discussing about this latest normal period. 1. The golden era of satellites: The latest normal period involves the era wherein space-based observations from both geostationary and polar orbiting satellites for a wide range of essential climate variables (ECVs), such as clouds, radiation, albedo, soil moisture, snow cover, and humidity, to name a few, are available [14; 15]. The WMO climate normals have traditionally been geared towards the in situ measurements of a few variables such as temperature and precipitation [1; 2]. The satellite sensors now provide information on more than two-thirds of all ECVs, and many of them do cover the entire 1991-2020 period [14; 15]. Furthermore, there have been stratospheric improvements in the retrievals of ECVs in the recent decades, uplifting their quality and maturity to a level where climate data records of ECVs are being provided [16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27]. The satellite observations could also provide climate normals globally, going well beyond the limited area coverage by the in situ measurements. The quality of reanalysis datasets has also been improving due to the assimilation of better observations. Thus, in principle, satellite-based climate data records and reanalysis could further complement one another to provide a global basis for climate normals. 2. Improved understanding of complex Earth system: The latest assessment reports from the Intergovernmental Panel on Climate Change (IPCC) outline the complexity of our Earth system and the feedbacks therein [28]. Our understanding of ECVs from the process to policy level has improved considerably in the last few decades. As we learn more and more about the importance of each climate variable in the Earth system, the demands for better information will increase from both the scientific community and the stakeholders. This means that in future, the climate normals for many ECVs would be needed. It is therefore clear that the satellite-based climate data records will play an increasingly important role in defining climate normals for a wide array of ECVs in future. But, computing climate normals from the climate data records is far from being easy and straightforward, and one needs also to understand how suitable and relevant WMO guidelines are for computing these normals. In the satellite community, the climatological averages provide the default basis to describe the state of the climate.