Climate Change
Climate change is a long-term shift in global or regional climate patterns, now driven mainly by human emissions of greenhouse gases from burning fossil fuels.
Definition
Climate change is a long-lasting shift in Earth's usual weather patterns, and today the planet is warming mainly because burning coal, oil, and gas adds heat-trapping gases to the air. Natural causes such as volcanic eruptions, changes in solar output, and slow shifts in Earth's orbit drove past climate swings including the ice ages, but current warming is attributed to human activity through several independent lines of evidence: the isotopic signature of fossil carbon in atmospheric $CO_2$, a pattern of warming in the troposphere alongside cooling in the stratosphere, and greater warming at night and in winter than natural cycles alone would produce. Global mean surface temperature has risen about $1.1$ to $1.2^\circ C$ above the 1850 to 1900 baseline, with the ocean absorbing over $90\%$ of the added heat, and ice cores show today's $CO_2$ level above $420$ ppm is unprecedented across the last $800{,}000$ years of glacial cycles.
Example
Earth has warmed a bit over $1^\circ C$ since the late 1800s, which sounds small but is enough to melt glaciers, raise sea levels, and make heat waves more common, and along the Outer Banks sea level is rising faster than the global average with more frequent sunny-day flooding. Warmer ocean water fuels stronger hurricanes such as Florence in 2018, which dumped record rainfall on North Carolina, and globally, sea level has risen about $20$ to $25\ \text{cm}$ since 1900 from thermal expansion and melting ice, with the rate roughly doubling in recent decades to over $4\ \text{mm/yr}$.
Key Insight
Climate change does not mean every day is hotter; it means the average shifts, so extreme heat, heavy rain, and strong storms all happen more often than before, and today's warming is occurring at least ten times faster than the change that ended the last ice age. The closest geologic analog is the Paleocene-Eocene Thermal Maximum about $56$ million years ago, when a rapid carbon release warmed the planet $5$ to $8^\circ C$ and acidified the oceans, with recovery taking over $100{,}000$ years, the same slow timescale of silicate weathering that makes today's change effectively permanent on human timescales.