User:Hedgehoque/sandbox

Lead additions
A global warming of 1.5 °C could already be reached in 2028. Beyond this level the risk of an irreversible impact increases.

In the short term, global warming can only be mitigated by a substancial drop in emissions. This requires the substitution of fossil fuels by large-scale capacities of renewable energy in electricity, transport and the heat sector. Levelised costs of wind energy and solar photovoltaics are increasingly out-competing coal, gas and nuclear power but require energy storage or power superhighways for a constant supply in a 100% sustainable scenario.

Mitigation
Climate change can be mitigated through the reduction of greenhouse gas emissions or the enhancement of the capacity of carbon sinks to absorb greenhouse gases from the atmosphere. The main challenge is the substitution of fossil fuels in electricity, transport and the heat sector which count for more than 70% of greenhouse gas emissions. . The massive price drops for renewable energy offer a chance to reduce oil, gas and coal.

Immediate steps to reduce GHG emissions:


 * Accellerated installation of wind energy, solar photovoltaics, concentrated solar power and hydroelectricity (at least six-fold compared to current plans).
 * A super grid of long distance HVDC power lines can transfer energy with low losses of only 1.5% per 1000 km from areas with a high potential for renewable energy to demand centres. A large network can guarantee supply in hours when wind and sun are not available locally. China supports the idea of a global, intercontinental grid. For a super grid in the USA, a study predicted 80% less GHG emissions.
 * Energy storage systems allow an independent, reliable supply for a limited network. Power-to-gas or the conversion to hydrogen can be produces without limits but reduce efficiency down to 30-40%. Batteries are more efficient but have a limited capacity. The environmental impact of their production must be improved. A study by the Imperial College of London calculated the lowest levelised cost of different systems. In 2020, pumped hydro (PHES), compressed air (CAES) and Li-on batteries are most cost effective depending on charging rhythm. For 2040, a more significant role for Li-on and hydrogen are projected.
 * Electrification of vehicles and the heat sector (with efficient heat pumps)
 * Energy conservation and increased energy efficiency
 * Load management of industrial energy consumption can help to balance the production of renewable energy production and its demand
 * less meat consumption would lower methane emissions.
 * Carbon pricing by tax and carbon emissions trading.

Mid-term effects can be achieved by: 

Controversial approaches include:
 * the enhancement of the capacity of carbon sinks to absorb greenhouse gases from the atmosphere by reforestation and preventing deforestation.


 * An increased use of nuclear energy : Apart from the risk of nuclear disasters and attacks, the disposal of radioactive waste can cause environmental damage and costs over more than one million years. Separated plutonium could be used for nuclear weapons.
 * Negative emissions by carbon capture and storage are part of many IPCC scenarios though CCS is energy intensive and expensive.

Geopoliticial Impacts of an Energy Transition
In 2019, oil and gas companies were listed by Forbes with sales of US$ 4.8 trillion, about 5 % of the global GDP. . Net importers such as China and the EU would gain advantages from a transition to low-carbon technologies driven by technological development, energy efficiency or climate change policy, while Russia, the USA or Canada could see their fossil fuel industries nearly shut down. . On the other hand, countries with large areas such as Australia, Russia, China, the USA, Canada and Brazil and also Africa and the Middle East have a potential for huge installations of renewable energy. The production of renewable energy technologies requires Rare-earth elements with new supply chains. A 2015 report by Citibank concluded that transitioning to a low-carbon economy would yield a positive return on investments.