Climate change is one of the greatest societal challenges of the 21st century. The dominant source of global warming is the increase of anthropogenic greenhouse gases in the Earth`s atmosphere. atmosphere. The two most important of those species are carbon dioxide (CO2) and methane (CH4). Together they account for ~82% of the anthropogenic radiative forcing. However, uncertainties in our knowledge of the budgets of these gases, which are determined by their sources and sinks, as well as inadequately understood feedback mechanisms, limit the accuracy of current climate change projections from the local to the global scale. To reliably predict the climate of our planet, and to guide political conventions on greenhouse gas avoidance, adequate knowledge of the sources and sinks of these greenhouse gases, their feedbacks, and the quantification of natural versus anthropogenic fluxes is mandatory. Wetland emissions of methane constitute the largest single source of methane to the atmosphere, even when considering all anthropogenic emissions, and are the most uncertain part of the budget. After the tropics, the largest distribution of wetlands is in the Arctic. The Arctic is warming twice as fast as compared to the global average, making climate changess polar effects more intense than anywhere else in the world. The Arctic accounts for nearly 50% of all organic carbon stored in the planetss soil but rising temperatures and thawing permafrost threatens its stability. The main objectives and tasks of MethaneCAMP are to: Collaborate and coordinate with the AMPAC (Artic Methane and Permafrost Challenge) initiative and forming AMPAC network aiming to contribute to bottom:up and top-down estimates of changes in methane emissions in the Arctic. Prepare a high-latitude-focused assessment of current atmospheric CH4 retrievals from medium spatial resolution and high spatial resolution instruments. Identify the improvement potential for high-latitude retrievals of CH4, test and validate these improvements and synthesize the potential of joint strategies. Analyse the changes in the Arctic CH4 with specific focus on i) quantifying longer:term trends, ii) identifying hot spots directly from observations, and iii) studying the apportionment between biogenic and anthropogenic CH4 sources by employing multi-scale Arctic CH4 observations in inverse modelling.

Polar stratospheric clouds (PSCs) play a central role in the formation of the ozone hole in the Antarctic and Arctic. PSCs provide surfaces upon which heterogeneous chemical reactions take place. These reactions lead to the production of free radicals of chlorine in the stratosphere which directly destroy ozone molecules. PSCs form poleward of about 60°S latitude in the altitude range 10 km to 25 km during the winter and early spring. The clouds are classified into Types I and II according to their particle size and formation temperature. Type II clouds, also known as nacreous or mother-of-pearl clouds, are composed of ice crystals and form when temperatures are below the ice frost point (typically below -83°C). The Type I PSCs are optically much thinner than the Type II clouds, and have a formation threshold temperature 5 to 8°C above the frost point. These clouds consist mainly of hydrated droplets of nitric acid and sulphuric acid. Despite two decades of research, the climatology of PSCs is not well described, and this impacts on the accuracy of ozone depletion models. The timing and duration of PSC events, their geographic extent and vertical distributions, and their annual variability are not well understood.The Davis lidar has been used to study stratospheric clouds since 2001. The observations consist of profiles of Rayeligh laser backscatter at a wavelength of 532 nm as a function of altitude. The measurements are being used to investigate the climatology of the clouds and their relation to the temperature structure of the stratosphere, and the influence of atmospheric gravity waves and planetary waves in modulating their structure and ozone depletion.

Sentinel-2 is a constellation of two optical imaging satellites, which are a part of Copernicus - the European Union's Earth observation program.

Albedo is the ratio of the radiation (radiant energy or luminous energy) reflected by a surface to that incident on it. Snow and cloud surfaces have a high albedo, because most of the energy of the visible solar spectrum is reflected. Vegetation and ocean surfaces have low albedo, because they absorb a large fraction of the energy. Clouds are the chief cause of variations in the Earth's albedo.The land surface albedo is the ratio of the radiant flux reflected from Earth's surface to the incident flux. It is a key forcing parameter controlling the partitioning of radiative energy between the atmospheric and surface. In the case of vegetation, a reference surface is typically defined at or near the top of the canopy and must be specified explicitly. Surface albedo depends on natural variations, highly variable in space and time as a result of terrestrial properties changes, and with illumination conditions and human activities and is a sensitive indicator of environmental vulnerability.

Launched in June 2008, Jason-2, also referred to as the Ocean Surface Topography Mission (OSTM), was the follow-on mission from Jason-1 and Posiedon/TOPEX. In this mission, the National Aeronautics and Space Administration (NASA) and Centre National d'Etudes Spatiales (CNES) worked collaboratively with the National Oceanic and Atmospheric Administration (NOAA) and European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) to extend the existing time series of ocean surface topography measurements. Jason-2 successfully obtained a continuous record of observations in line with previous missions which included measurements of time-averaged ocean circulation, global sea-level change and improved open ocean tide models, until it was decommissioned in October 2019.

Point product containing a cloud of elevations with an associated uncertainty in geo spatial units. The thematic point product is published on a monthly basis once the Uncertainty calculation is complete.

The project will deliver the first measurements of Arctic sea ice thickness during summer months, from twin satellites- ESA s CryoSat-2 & NASA s ICESat-2. Research linked to LPF project ArcticSummIT (https://eo4society.esa.int/projects/arcticsummit-arctic-summer-ice-thickness/)

Develop and validate different approaches to retrieve snow thickness over the sea ice, to develop a new prototype processor, and to produce and validate an experimental dataset of snow thickness over the Arctic.

Difference of sea surface height and mean sea surface. Sea surface height may be corrected using models for effects such as tides and atmospheric forcing

There are no Arctic-wide or Antarctic-wide measurements of the volume of sea ice, but the volume of the Arctic sea ice is calculated using the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) developed at the University of Washington Applied Physics Laboratory/Polar Science Center. PIOMAS blends satellite-observed sea ice concentrations into model calculations to estimate sea ice thickness and volume. Comparison with submarine, mooring, and satellite observations help increase the confidence of the model results