Anthropogenic vs natural causes of climate change

This is two questions wearing one prompt, and they need different kinds of answer. The first is expository — explain the difference between anthropogenic and natural causes — and can be answered from the science. The second is a **classification with a superlative in it**: do you class climate change as *the major* environmental health challenge of the 21st century. That word 'major' is comparative, so an answer that only describes climate harms has not addressed it. To classify something as the biggest you have to name what it is bigger than, and the serious rivals are specific: household and ambient air pollution, unsafe water and sanitation, and antimicrobial resistance. Pick a position and defend it against at least one of them. Naming the rival in your opening sentence also stops the post drifting into a general description of climate harms, which is where the word minimum usually gets filled.

On the first question, the mistake to avoid is overcorrecting into 'natural causes are irrelevant'. They are not — orbital and rotational variation, solar output, albedo, volcanic activity and natural carbon fluxes are real forcings, and they explain climate change perfectly well for the period before the Industrial Revolution. The precise claim, and the one that earns marks, is narrower: natural causes cannot explain the warming observed since the mid-twentieth century. Framing it that way lets you take the natural forcings seriously rather than waving them away, which is both better science and a stronger argument, because it engages the objection instead of ignoring it. It also protects you from the obvious rebuttal, since a reader who knows the natural forcings will notice if you have pretended they do not exist.

Two specific figures do most of the work in that argument and are worth quoting rather than paraphrasing. First, solar: since 1750 the average energy arriving from the Sun has stayed constant or decreased slightly, while global temperature has risen — so the obvious natural candidate moves the wrong way. Second, volcanoes: human activity releases more than a hundred times as much carbon dioxide each year as volcanoes do, which disposes of the common claim that a single eruption outweighs industry. Add that atmospheric CO₂ has risen by roughly half since 1750, and you have an attribution argument built from three checkable numbers rather than from consensus statements. Quoting the figure with its baseline year matters, because the whole force of the solar point is that it runs the opposite way to temperature over the same period.

The second question is framed as *environmental health*, not climate science, and answers routinely drift into sea level and species loss. Keep the evidence on human health outcomes: 3.6 billion people already living in areas highly susceptible to climate change; an estimated 250,000 additional deaths a year between 2030 and 2050 from undernutrition, malaria, diarrhoea and heat stress; roughly 37% of heat-related deaths already attributable to human-induced warming; heat deaths among over-65s up 70% in two decades. Those are health figures, they are attributable, and they are what the question is actually asking you to weigh. Each of those is attributable rather than merely correlated, which is exactly what a claim about causes needs.

The strongest way to resolve the superlative is to reach for the *threat multiplier* framing rather than arguing climate change is a bigger single cause of death than air pollution — a claim that is hard to defend head-on. Climate change is not a competing disease; it worsens the challenges already on the list, driving heat stress, extending the range of vector-borne disease, damaging food and water security, and hitting the least resilient hardest — death rates from extreme weather in vulnerable regions ran fifteen times higher than in less vulnerable ones over the past decade. That lets you argue it is the major challenge *because* it acts on all the others, which is a defensible position rather than a ranking exercise. It also matches how the health agencies themselves frame it, so the position has institutional backing rather than resting on your own arithmetic.