Your question, “How do we know it’s us causing the warming and not natural causes?” intrigues me, as it is a question that I, too, have been ruminating over for quite some time…From what I’ve been reading/writing/thinking about concerning climate change denial/deniers, I want to point to two insights: First, I want to refer to Meadows, Meadows, and Randers’ “Limits to Growth,” more specifically, the authors’ list of what we’re certain of regarding climate change. The authors confirm that we’re certain that “human activities contribute to an increase in greenhouse gas concentration” (118). Shouldn’t we re-frame climate change conversations so that they support this certainty? But even if we disagreed with Meadows, Meadows, and Randers’ assertion, and chose to believe that we are UNcertain about the effect of human activities on greenhouse gas concentration, would it really be worth delaying – and perhaps preventing – policymakers from acting in response to the situation: the situation being that the earth is warming? In the end, it seems as though we have more than enough science to support global warming, but that we neglect the savviness to communicate those findings in a way that effectively convinces people to change their behavior in response to changes in the earth’s temperature. Perhaps the denial occurs as a response to the confusion that ensues from the ambiguous and often contradictory terminology that is being used to communicate climate change to the public. Perhaps we need to implement incentives for behavior that is responsive to climate change? Do we need a better understanding of climate change or a more effective means of disseminating consistent information, incentivizing positive responses to climate change, and managing climate change policy through the lenses of science AND public values?
Regarding the answer to your question, “Because we’ve directly measured it,” I see the logic in providing proof, especially in the sense that the purpose of the article is to identify THE question that seems to incite the most widespread doubt about climate change: whether humans are the primary cause or not. Your answer – that we have directly measured it – makes logical sense, and I certainly agree. However, I also want to suggest the following: first, that measurements aren’t always consistent across time, and therefore could “backfire” if a purported measurement ebbs and flows throughout time, deniers could claim that no changes in human behavior led to a decrease in impact… secondly, that we ought to be moving away from “directly measuring” and toward enabling a more effective management of uncertainties…hypothetically, even assuming ALL climate change science is uncertain we are still obligated to invest ourselves not in the application of science funding for the “discovery” of climate change “facts,” but to the experimentation of climate change scenarios… it seems to me as though this is the only segue to action… if we languish in fact-finding and directly measuring, climate change conversations easily become circular; delaying policy. If we engage in experimentation – even in the face of uncertainty – we will be better able to manage the real scenario: the warming of the earth and the consequences that ensue as a result.