Greenhouse gas systems. Future warming is projected to have a range of impacts, including sea level rise, increased frequencies and severities of some extreme weather events, loss of biodiversity, and regional changes in agricultural productivity. The main sources of greenhouse gases due to human activity are: The seven sources of from fossil fuel combustion are (with percentage contributions for 2000–2004): Carbon dioxide, methane, nitrous oxide () and three groups of fluorinated gases (sulfur hexafluoride (), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs)) are the major anthropogenic greenhouse gases, and are regulated under the Kyoto Protocol international treaty, which came into force in 2005. Emissions
Acidic oxide Some non-metal oxides, such as nitrous oxide (NO) and carbon monoxide (CO), do not display any acid/base characteristics. Acidic oxides can also react with basic oxides to produce salts of oxoanions: Acidic oxides are environmentally relevant. Sulfur and nitrogen oxides are considered air pollutants as they react with atmospheric water vapour to produce acid rain. Although it is difficult to classify these oxides as acids, the property is manifest in reactions with bases. For example, carbon dioxide reacts with alkali. For this reason, alkali is kept in stoppered vessels to inhibit reaction with atmospheric carbon dioxide. In geochemistry complex silicates