&quot;Runaway greenhouse effect&quot; is what could happen if the methane deposits in the Arctic Siberian tundra are released to the atmosphere. See [1] for more information.<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Arctic_methane_emissions" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Arctic_methane_emissions</a><p>Edit: if it&#x27;s not obvious, &quot;runaway effect&quot; is another term for &quot;positive feedback loop&quot;. The first paragraph of the linked article reads:<p>&gt; Arctic methane release is the release of methane from seas and soils in permafrost regions of the Arctic, due to deglaciation. While a long-term natural process, it may be exacerbated by global warming. <i></i>This results in a positive feedback effect, as methane is itself a powerful greenhouse gas.<i></i>