XplaiNLP @ ClimateCheck 2026 Task 2: Comparing Hierarchical Approaches for Fine-Grained Climate Disinformation Narrative Classification

Arthur Hilbert, Jing Yang, Vera Schmitt


Abstract
We present our submission to Task 2 of the ClimateCheck 2026 shared task on Disinformation Narrative Classification which requires assigning climate-contrarian claims to fine-grained disinformation narratives. Using Qwen3-8B as a fixed backbone, we systematically compare data augmentation, prompt engineering and reinforcement learning techniques. Our experiments show that structured reasoning, particularly a chain-of-thought (CoT) prompting strategy aligned with the taxonomy’s hierarchical structure, substantially improves Macro-F1 over both zero-shot baselines and augmentation-based fine-tuning. Our best configuration achieves 0.625 Macro-F1, ranking first in Task 2. Our findings demonstrate that carefully designed hierarchical prompting can rival more complex training interventions in low-resource, highly imbalanced narrative classification settings.
Anthology ID:
2026.nslp-1.29
Volume:
Proceedings of Natural Scientific Language Processing (NSLP) @ LREC 2026
Month:
May
Year:
2026
Address:
Palma, Mallorca (Spain)
Editors:
Georg Rehm, Stefan Dietze, Danilo Dessi, Diana Maynard, Sonja Schimmler
Venues:
NSLP | WS
SIG:
Publisher:
ELRA Language Resources Association (ELRA)
Note:
Pages:
289–296
Language:
External URL:
https://lrec.elra.info/lrec2026-ws-nslp-29
DOI:
10.63317/4ufq9w234tkf
Bibkey:
Cite (ACL):
Arthur Hilbert, Jing Yang, and Vera Schmitt. 2026. XplaiNLP @ ClimateCheck 2026 Task 2: Comparing Hierarchical Approaches for Fine-Grained Climate Disinformation Narrative Classification. In Proceedings of Natural Scientific Language Processing (NSLP) @ LREC 2026, pages 289–296, Palma, Mallorca (Spain). ELRA Language Resources Association (ELRA).
Cite (Informal):
XplaiNLP @ ClimateCheck 2026 Task 2: Comparing Hierarchical Approaches for Fine-Grained Climate Disinformation Narrative Classification (Hilbert et al., NSLP 2026)
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