La Niña’s Unexpected Impact on Global Temperatures

The global average surface air temperature reached a record high of 1.75 degrees Celsius above pre-industrial levels. This spike occurred despite the onset of La Niña conditions, which typically cool global temperatures. This unusual situation has raised concerns among climate scientists about the effectiveness of natural cooling mechanisms in moderating global warming.

About La Niña

La Niña is part of the El Niño Southern Oscillation (ENSO). ENSO consists of three phases – El Niño, La Niña, and a neutral phase. La Niña is characterised by cooler sea temperatures in the central and eastern tropical Pacific. This phase typically strengthens trade winds, pushing warmer water towards the western Pacific and allowing cooler water to surface in the east. These changes influence global weather patterns and can affect regional climates .

ENSO’s Phases and Their Effects

Each ENSO phase has distinct impacts on global temperatures. During El Niño, warmer waters elevate global temperatures. Conversely, La Niña usually results in cooler temperatures. However, the effects can vary widely by region and time. The unique characteristics of each La Niña cycle, including its intensity and duration, mean that not all cycles produce the same climatic outcomes.

Why La Niña Failed to Cool January 2025

The La Niña phase that emerged in December 2024 was relatively weak. Experts anticipated a stronger phase, which typically would have provided a more cooling effect. Factors contributing to this weakness include delayed onset and insufficient time for the phenomenon to strengthen before the peak winter months. Additionally, high levels of greenhouse gases in the atmosphere continued to trap heat, counteracting any cooling effects from La Niña.

Role of Atmospheric Carbon and Aerosols

Atmospheric carbon levels reached unprecedented heights in early 2025. The continuous rise in greenhouse gases has overshadowed the potential cooling from La Niña. Furthermore, a reduction in aerosols due to clean air policies has diminished their natural cooling effects. Aerosols typically scatter solar radiation, helping to lower temperatures. Their absence means that less sunlight is reflected away from the Earth’s surface, contributing to higher temperatures.

Implications for Climate Change

The inability of La Niña to produce expected cooling marks a concerning trend. It suggests that natural climate regulation mechanisms may be weakening. This situation puts stress on the urgency for substantial reductions in greenhouse gas emissions to mitigate the ongoing rise in global temperatures. Without action, the potential for natural phases to provide relief from warming may diminish further.

Questions for UPSC:

1. Critically analyse the role of the El Niño Southern Oscillation in global climate patterns.
2. Explain the significance of greenhouse gas emissions in relation to climate change. How do they impact global temperature trends?
3. What are the characteristics of the La Niña phase? Discuss its potential effects on regional climates.
4. With suitable examples, comment on the relationship between aerosol levels and global temperature changes.

Answer Hints:

1. Critically analyse the role of the El Niño Southern Oscillation in global climate patterns.

1. ENSO consists of three phases – El Niño, La Niña, and neutral, each affecting global weather differently.
2. El Niño typically leads to warmer global temperatures due to weakened trade winds and warmer ocean waters.
3. La Niña usually results in cooler global temperatures by strengthening trade winds and promoting upwelling of cold water.
4. ENSO influences precipitation patterns, storm activity, and droughts in various regions worldwide.
5. The irregular cycles of ENSO (2-7 years) contribute to climate variability, complicating long-term climate predictions.

2. Explain the significance of greenhouse gas emissions in relation to climate change. How do they impact global temperature trends?

1. Greenhouse gases (GHGs) trap heat in the atmosphere, leading to an increase in global temperatures.
2. High levels of GHGs in 2024 and early 2025 contributed to record-breaking temperature spikes despite La Niña conditions.
3. GHG emissions primarily come from human activities such as fossil fuel combustion, deforestation, and industrial processes.
4. Increased atmospheric GHG concentrations disrupt natural climate regulation mechanisms, diminishing their cooling effects.
5. Mitigating GHG emissions is crucial to slowing down climate change and stabilizing global temperatures.

3. What are the characteristics of the La Niña phase? Discuss its potential effects on regional climates.

1. La Niña is characterized by cooler sea surface temperatures in the central and eastern tropical Pacific.
2. It strengthens trade winds, pushing warm water towards the western Pacific and allowing cold water to surface in the east.
3. Typically, La Niña brings increased rainfall to regions like Southeast Asia and Australia, while causing drier conditions in the Americas.
4. The intensity and duration of La Niña can vary, leading to different regional climate impacts each cycle.
5. Weak La Niña phases may have less pronounced cooling effects, as seen in January 2025.

4. With suitable examples, comment on the relationship between aerosol levels and global temperature changes.

1. Aerosols scatter solar radiation, which can lead to cooling effects on the Earth’s surface.
2. Reduction in aerosol levels due to clean air policies can contribute to increased temperatures, as less sunlight is reflected away.
3. For example, the decline in aerosols during the COVID-19 pandemic led to noticeable temperature increases in some regions.
4. Conversely, high aerosol concentrations can lead to cooler temperatures, particularly in regions affected by industrial emissions.
5. The interplay between aerosol levels and greenhouse gases is critical in understanding short-term climate variability.