Dr. Vincent Ojeh
Many people have observed that despite being in the traditional harmattan season, the familiar cold mornings, dry air, and thick dusty haze are largely missing.
This is not a coincidence or a false perception. It reflects real changes within the West African climate system, driven by both natural variability and long-term climate change.
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Under normal conditions, harmattan occurs during the boreal winter when strong high-pressure systems form over the Sahara Desert.
These systems generate cool, dry north-easterly winds that carry dust southward across West Africa. At the same time, the Intertropical Discontinuity (ITD)the boundary separating dry continental air from moist maritime air—moves far south of Nigeria.
This allows dry air to dominate, producing cold nights, low humidity, dry skin, and poor visibility.
This year, however, that mechanism appears weakened. One major reason is the rapid warming of the Sahara Desert linked to global climate change.
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As the Sahara warms, the temperature contrast between the desert and the Gulf of Guinea reduces. This contrast is essential for driving strong harmattan winds.
When it weakens, the winds become less intense, irregular, or short-lived, causing harmattan to arrive late, appear briefly, or fail to establish fully.
Another key factor is the behaviour of the Intertropical Discontinuity. In recent years, the ITD has tended to remain farther north than expected during the dry season.
This allows moist Atlantic air to penetrate deeper into Nigeria, increasing humidity, cloud cover, and warmer nighttime temperatures.
As a result, classic harmattan conditions are suppressed even when the season suggests they should be present.
Additionally, sea surface temperatures in the Gulf of Guinea have been warmer than normal. Warmer waters enhance evaporation and increase the moisture transported inland by south-westerly winds.
This moisture competes with—and often overwhelms—the dry harmattan flow, leading to conditions that feel neither cold nor dry.
In such cases, only a light haze may appear, without the sharp chill and dryness associated with harmattan.
Dust availability also plays a critical role. Harmattan haze depends not just on wind direction, but on the presence of loose dust in the Sahara and Sahel.
Changes in land use, vegetation cover, and rainfall patterns are reducing dust mobilisation in these regions.
When soils are damp or stabilised by vegetation, less dust is lifted into the atmosphere, even if winds are present. This keeps visibility relatively clear and makes harmattan seem absent.
All these factors occur within a broader pattern of increasing climate variability across West Africa. Seasons are becoming less predictable, with delayed onset, shorter duration, and frequent interruptions.
Instead of a continuous harmattan lasting several weeks, we now experience brief episodes broken by warm or humid conditions—one of the clearest climate-change signals in the region.
In conclusion, harmattan is not disappearing, but it is becoming increasingly unreliable. Weakened pressure systems, persistent moist air, warmer oceans, reduced dust mobilisation, and rising climate variability are reshaping the season.
What we are witnessing is not an isolated abnormal year, but part of a broader climatic transition with serious implications for agriculture, public health, aviation, and environmental planning across Nigeria and West Africa.
Dr. Vincent Ojeh
Taraba State University