Developing El Niño conditions, now officially declared with strengthening sea-surface temperature anomalies across the equatorial Pacific, represent the dominant near-term driver pushing June 2026 global mean surface temperature anomalies toward the 1.15–1.19 °C range above the 1850–1900 baseline. Long-term anthropogenic warming provides the elevated baseline, while the emerging event—forecast by NOAA and WMO ensembles to intensify through late 2026—adds positive forcing that historically elevates monthly anomalies by 0.1–0.2 °C during onset phases. Recent 2025 observations near 1.19 °C and early June 2026 Pacific heat-content surges align with this central outcome; model consensus and historical analogs limit downside risk below 1.10 °C while capping upside above 1.24 °C absent rapid further intensification.