River Liming

Oceans play an important role in global heat transfer and carbon storage processes. As global temperatures and atmospheric carbon levels rise, some have suggested artificially modifying the vertical movement of water to enhance these processes.

In many Arctic and Northern regions, domesticated or semi-domesticated reindeer (Rangifer tarandus) are the only large herbivores (Uboni et al. 2016). Reindeer play a crucial role in these ecosystems and in the livelihoods and traditions of multiple local and indigenous populations. In light of the major impact of climate change in the Arctic, the capacity of large herbivores to mitigate some of these effects is being explored. Herbivores can have different climate positive effects as they can reduce shrubification and slow ecosystem responses to climate change (Olofsson and Post 2018; Happonen et al. 2021), modify summer and winter surface albedo (te Beest et al. 2016), trample winter snow to thicken permafrost (Beer et al. 2020; Windirsch et al. 2022), and increase biomass and soil carbon sequestration (Ylänne et al. 2018; Ylänne et al. 2021; see also soil management).

GHG emissions reductions and future negative emissions are the only sustainable solutions to stabilize or even reverse global warming as they counter the cause of the problem. However, such actions will likely take a while to materialize, and inertia in the climate system and “baked-in” warming already ensures major changes in global temperatures and the nearing of several tipping points. Solar radiation management (SRM) techniques seek to reduce global temperatures by reflecting incoming solar radiation. They would thereby not fix the underlying issue of the warming effects of GHGs, but are according to the United Nations Environment Programme (UNEP) Review on Solar Radiation Modification Research (2023) ‘the only known approach that could be used to cool the Earth within a few years’.

Roughly one-third of the incoming solar radiation is directly reflected back into space by the Earth’s atmosphere and surface albedo. Clouds play an important role in this, although their role is double as water droplets can also interfere with outgoing longwave radiation, thereby contributing to the greenhouse effect. Over open water clouds can make a particularly big difference as the albedo of the water is below 0.1, thereby absorbing most of the sun’s energy.

The majority of the inorganic carbon on Earth is stored in the oceans. There is a natural carbon exchange between the ocean and the land.

Wetlands and peatlands play important roles in global carbon cycles. Wetlands are areas that are seasonally covered by water. Globally mangroves are often the main topic of focus when it comes to wetlands (IPCC AR6 WG3, 2022, 7.4.2.8). In the Arctic and Northern regions, peatlands are important wetland elements, and will be the focus of what follows. Such peatlands are very carbon rich and store carbon in biomass below and above ground and in soil carbon. Although they only make up 3% of the Earth’s surface, peatlands store up to 21% of terrestrial carbon, and damaged peatlands contribute close to 5% of anthropogenic CO2 emissions (Leifeld et al. 2019). Peatland drainage between 1850 and 2015 has globally already released 80 Gt CO2-eq, and this figure may climb to 250 Gt CO2-eq by 2100 (Leifeld et al. 2019).

Compared to the global state of such areas, Arctic and Northern wetlands and peatlands remain relatively intact (UNEP 2021), and only around 2% of boreal peatlands are currently converted into croplands (Leifeld and Menichetti 2018). However, increasing attention is being paid to the importance of restoring destroyed areas, which make up 78% of total global peatlands, and preserving endangered ones, especially in light of the effects of climate change on such ecosystems. The Resilience and Management of Arctic Wetlands notes (CAFF 2021) therefore highlight the need for increased wetlands resilience to protect against future damage.

Large areas of the Northern and Arctic regions consist of permafrost, almost permanently frozen soil. As global temperatures rise, these permafrost areas are thawing at an ever faster rate. This thawing leads to massive amounts of GHGs being released into the atmosphere, as carbon stored in the permafrost is converted into methane by bacteria. Because methane is a very potent GHG, the thawing of the permafrost is considered a major tipping point in the climatic system. Permafrost preservation is of the utmost importance because Arctic terrestrial regions alone hold up to 1500 Pg C (Schuur et al. 2015), and although there is large uncertainty about the total amount of emissions from permafrost (Miner et al. 2022), especially when it comes to nonlinear abrupt thawing (Turetsky et al. 2020), significant amounts of carbon release is to be expected as the Northern regions warm.

Up to 50% of the world’s glaciers are set to disappear this century, with many more at risk if emission reduction targets are not met (Rounce et al. 2023).