Scientists use multiple lines of evidence to demonstrate that climate change is occurring, drawing from a wide range of observations and data sources.

1. **Temperature Records**: Historical temperature records show a clear trend of global warming over the past century, with the last few decades being the warmest on record. Data from land-based weather stations, ocean buoys, and satellite measurements confirm this increase.

2. **Glacial and Ice Cap Melting**: The rapid melting of glaciers and ice caps in regions like Greenland and Antarctica provides stark evidence of rising global temperatures. Satellite imagery and field measurements document the shrinking ice masses and their contribution to sea-level rise.

3. **Sea-Level Rise**: Tide gauge measurements and satellite data indicate that global sea levels have risen significantly in the past century. This rise is primarily due to thermal expansion of seawater as it warms and the addition of water from melting ice sheets and glaciers.

4. **Ocean Acidification**: Increased CO2 levels in the atmosphere are leading to higher concentrations of dissolved CO2 in oceans, causing ocean acidification. This change in ocean chemistry is evidenced by changes in marine ecosystems, such as coral bleaching.

5. **Extreme Weather Events**: The increasing frequency and intensity of extreme weather events, such as hurricanes, heatwaves, and heavy precipitation, are linked to climate change. Climate models and observational data show that these changes are consistent with expected outcomes of a warming planet.

Together, these lines of evidence provide a robust and comprehensive picture of ongoing climate change, underscoring the urgent need for action.